DEAR ABBY: When I was barely 17 years old, I went with a very pretty girl who had a reputation for being easy. She wanted me to go all the way with her and I almost did; then she dropped me for a guy who was more "mature" (her words).

About three months later, on a hot summer night, she drove over to my house in a borrowed car (her brother's) and took me for a drive. She seemed very glad to see me and said things like, "I can't seem to get you out of my mind." We parked by the lake and she started to kiss me and rub me all over. She got me real excited and practically tore my clothes off. I told her I wasn't prepared for sex, so she said, "Don't worry - I'm on the pill." The whole thing didn't take 10 minutes. It all happened so fast I was almost in shock.We saw each other almost every weekend for about a month, and then she told me she was pregnant! I was a senior in high school and was in no position to get married, but I had to tell my folks. They got together with her folks and we had a quick wedding.

Well, five months later she had a baby. Now I realize she knew she was pregnant when she got me to have sex with her. The baby wasn't mine but I have to support "our" son until he is 18 because the law says I am the father. This mess blew my whole future.

I got a job parking cars and have had to forget about college for now. Maybe this letter will keep some other guy from being the kind of jerk I was. - STUCK IN A SMALL TOWN

DEAR STUCK: You and your parents should discuss this with an attorney. Perhaps you are not as "stuck" as you think you are. There are tests that can prove whether or not you are the baby's father. A blood sample from the baby and another from you is all that's necessary.

DEAR ABBY: I wish you would print this for all fat wives to see: Do all you fat wives who have gained a lot of weight since your marriage believe your husbands when they say, "It's OK, honey, there's just that much more of you to love"?

When hubby's eye begins to wander, you can bet it's not toward another fat woman; it's a gal with a trim figure.

Women, don't let yourselves go! I did and nearly lost my husband. Thank heavens, I woke up just in time. - FORMERLY FAT PHYLLIS

DEAR FORMERLY FAT: Why limit the suggestion to women only? Plenty of fat men have gone under for the third time while their wives were eyeing the lifeguard.

DEAR ABBY: Why all the fuss about being addressed by one's first name instead of "Mrs. So-and-so"?

In biblical times, apparently there were no last names - and if Matthew, Mark and Luke and Mary and Sarah and Ruth were good enough then, it's certainly good enough for me now.

Also, today, with so many women in executive positions, I'm sure they are all on a first-name basis with their co-workers. To me, it just seems friendlier. - TRUDY IN INDIANA

DEAR TRUDY: Most - but not all - business and professional women (like men) have no objection to being addressed by their first names. However, it is presumptuous to assume that such familiarity is acceptable to everyone. When in doubt, and especially on first being introduced, it's wise to ask, "And what shall I call you?"

Want your phone to ring? Get Abby's booklet, "How to Be Popular" - for people of all ages. To order, send a long, business-size, self-addressed envelope, plus check or money order for $3.95 ($4.50 in Canada), to: Dear Abby, Popularity Booklet, P.O. Box 447, Mount Morris, IL 61054. (Postage is included.)