What was going on when I was born?

SUFFOLK COUNTY is catching up with Nassau County, at least as far as population is concerned. Sometime within the next 12 months, Suffolk is expected to draw even in the race. And while the number of people increase in the area, so do the number of elderly and one-person households, a trend that is similar to demographic changes taking place across the country, according to sociologists and governmental policy planners. The two-county area as a whole is expected to show a modest gain in its number of residents in 1983, reversing last year's trend, which showed a slight loss.

The Defense Department has recommended to President Reagan that he raise the number of American military advisers in El Salvador to 125 next year, more than doubling the current total, senior Administration officials said today. The Defense Department, according to the officials, has also proposed that the advisers be allowed to increase their mobility by accompanying Salvadoran forces into the field. But the department has recommended no change in the current policy that prohibits American servicemen from being involved in combat operations or working in combat zones. Mr. Reagan has the proposals under consideration but has not yet decided whether to approve them, the officials said. Some aides have warned Mr. Reagan that any rise in the Administration's self-imposed limit of 55 advisers in El Salvador could touch off serious opposition in Congress and might lead to the adoption of a legally binding limit.

''THE town is going to be discovered,'' Marguerite Dunscomb said regretfully, as she sat in a Somers coffee shop. ''As it is now, when you tell people where you live, they never heard of it.'' ''It will be good for the town,'' countered Patricia Testa, owner of Patty's Place. ''I've lived here all my life, and I get tired of this dead place.'' The two were considering what will happen two years from now, when two big corporations, International Business Machines and Pepsico, come to this rural town of 15,000 people.

The leader of the Druse minority in Lebanon announced today that he and a group of leftist and Syrianbacked leaders had created an alliance to oppose the Government of President Amin Gemayel. The Druse leader, Walid Jumblat, said the alliance, which he called the National Salvation Front, would administer areas in northern and eastern Lebanon now under the Syrian Army. Mr. Jumblat's forces have been engaged in heavy fighting near Beirut with Christian militia units of Mr. Gemayel's Phalangist Party. He said the front's leadership would consist of himself, former President Suleiman Franjieh, who is a Maronite Christian, and former Prime Minister Rashid Karami, a member of the dominant Sunni branch of Islam.

At a time when much of the rest of the country is trimming arts budgets and wondering whether major cultural institutions will survive, Texas is launching a new round of projects with huge price tags: a $75 million house for opera and ballet and a third major art museum in Houston, an art museum and a symphony hall in Dallas, and a music festival with aspirations to international stature in San Antonio. Is this just a matter of the ostentation of wealth -where money goes, culture will follow? Texas is proverbially rich, and the economic recession has hit the state belatedly and comparatively mildly, so the simplest explanation of the culture gusher is at least plausible - especially since These days, many of the Texans with the means to fund it, are beginning to consider culture not as a frill but as the potent sign of their own and their state's prestige. The push to make Texas a great cultural center is on - though the question of exactly how much actual creativity money can buy still remains.

After more than a year of intense activity, the Honduran-based rebels fighting the Nicaraguan Government have failed to achieve significant military gains or to cause a serious political threat to the Government, foreign diplomats and Nicaraguan officials here say. While the United States-backed rebels have harassed the Government and caused hundreds of civilian and military deaths and an estimated $70 million in damage, the officials say, they have been unable to hold any town or valuable territory here for any length of time. This reported lack of military success has deepened the Nicaraguan Government's fears that the Reagan Administration may now feel compelled to take harsher measures in its opposition to the Managua regime. Another key factor, as government officials see it, is that while economic sanctions imposed by Washington have hurt, they are not likely to paralyze the Nicaraguan economy for several years. This is in part because Nicaragua continues to receive assistance from the Soviet bloc and a number of Western European countries, including France.

NEW BRUNSWICK AS MANY as 8,000 people are expected to converge at Cook College Saturday for the annual Vegetable and Flower Open House there. If luck holds, the weather will be pleasant, just as it has been for every Open House since the first one in 1965. But rain or shine, the farm and gardens will be open from 8:30 A.M. to 3 P.M. Guests will be able to stroll through some 60 acres of landscaped gardens, have an opportunity to ask questions of more than 50 county agricultural agents and specialists and inspect the projects under way at the college's 75-acre Vegetable Research Farm. There have been years when attendance hit 12,000, with visitors coming not only from New Jersey but also from Pennsylvania, New York, Delaware and other nearby states. Although the Display Gardens are open to the public the year-round, this is the only day when it is invited to visit the Vegetable Research Farm or bring problems to plant clinics at both sites.

The Soviet intelligence and security agency, the K.G.B., has entered a phase of aggressiveness in its activities in the West, according to allied officials. The upsurge is cited as the principal cause of a series of expulsions of Soviet agents from countries around the world since the start of 1983. The number of Russians expelled for illegal intelligence-gathering so far this year has reached 90, according to the United States State Department. Six others, identified as spies, left on their own. The total for all of 1982, according to United States Government records was 49; in 1981, it was 27. The increased number of expulsions, including the French decision to order the departure of 47 Russians in April, is widely described as a function of the stepped-up K.G.B. effort, but not a result of a coordinated Western campaign.

A REDUCTION in the number of law secretaries serving the county's six Family Court judges, with the saving in salaries transferred to other sections of the Ninth Judicial District, is causing consternation among some judges and lawyers, who charge that the move is threatening the efficiency of the court. Judges have traditionally been entitled to have their own law secretaries - lawyers who review orders and motions, conduct legal research and draft opinions. But a two-year-old directive by the state's Chief Administrative Judge, which was recently put into effect in Westchester, provides for only one law secretary for every two Family Court judges - or three secretaries for the six judges. A spokesman for the state's Office of Court Administration, Harold Wolff, said the reduction reflected a ''general managerial policy to improve the efficient operation of the trial courts and to maximize limited resources.''

AUGUST By Judith Rossner. 376 pp. Boston: Houghton Mifflin Co. $15.95. LIKE Parisians, shrinks leave town in August. If they're New York shrinks, they flock to the Hamptons, where for one brief month no patients interrupt their lives. The patients, meanwhile, must fend for themselves. Along with the shorter breaks at Christmas and Easter, the recurrence of the August hiatus lends a rhythm to both sides of the psychoanalytic relationship. Enduring it or delighting in it, patient and analyst must somehow come to terms with August - the ritualized intrusion of time into the timeless world of the analytic session. Judith Rossner's new novel takes its title and form from this fact of psychoanalytic sociology. Famous as a clinician of disordered minds - most memorably in ''Looking for Mr. Goodbar'' and ''Emmeline'' - Mrs. Rossner now turns her attention to the scene where disorders are supposed to get rectified. In meticulous detail, she narrates the five-year analysis of Dawn Henley by Dr. Lulu Shinefeld, the one a blond New England teen-ager, the other a fortyish Jewish Manhattanite. In the ordinary course of things, two such different women would never meet, but there's nothing ordinary about analysis, and as the two women grow and change, they make permanent marks on each other's lives.Walter Kendrick, who teaches English at Fordham University, is the author of ''The Novel Machine.''

FALLS VILLAGE IN the recreation hall, Florence Muller and Jean Judashko were dancing to a Neil Sedaka record. In the lounge, Leon Schlam was playing chess. Selma Toback sat on the sun deck outside her room, writing postcards to friends and family back home in the Bronx. ''I say, 'Having a good time,' but not 'Wish you were here,' '' she said with a giggle. It was a typical day at a not-so-typical summer camp in the hills of northwestern Connecticut. While most camps stock candy and soda in their canteens, Camp Isabella Freedman in Falls Village does a brisk business in bananas, apples and prune juice, according to its executive director, Steven Terner. The camp is for the elderly, who arrive in buses from the New York City area every two weeks. The campers must be at least 60 years old and able to care for themselves. While their average age is 75, a few are considerably older. Mr. Schlam, who has come from his home in Manhattan to Camp Freedman for seven summers, will be 102 in November. He likes to play chess and make carved figurines, rarely misses a morning calisthenics session and walks three miles each day.

Since Temple Shaaray Tefila moved from its last home on the West Side in 1959 to its current location on the corner of East 79th Street and Second Avenue, its membership has nearly quadrupled. Consequently, quarters in its adjoining community house have been tight, to say the least.