Q. I need advice from someone who doesn't know me. I can't take my problem to my parents. They are very moralistic and religious and besides, I don't want to hurt them.

I am 17 and a high school senior. I have good grades and believe I can get into a good college. I want to go very much because I hope to be a doctor.

The problem is that my boyfriend and I made a stupid mistake and I'm pretty sure I'm pregnant. He has promised to stick by me but neither of us knows what to do. We are way too young to get married, but I don't think I could stand giving the baby away.

My father and mother say abortion is murder. My boyfriend says lots of people think abortion isn't murder and that it is the answer for us. I'm so scared I don't know what I think.

A. If you are pregnant -- and Planned Parenthood can give you a quick, dependable answer -- you must make several grave decisions as fast as you can.

Your first is not what to do but whether to tell your parents. You have no choice if you have the baby -- with or without marriage, or whether you arrange an adoption. They're bound to notice that you're pregnant.

Even if you choose abortion, it's usually better to tell the truth. Just as honesty strengthens the rock on which a relationship is built, so does deception fracture it, at least a little bit.

If you do decide to have the baby, you have some facts to face.

Although most pregnancies go well and most babies are healthy -- whatever the age of the mother -- teen-agers have more problems in pregnancy than any other age group, and their babies have more developmental problems. Not only is the pelvic cavity usually too small to accommodate a baby easily until the mother is about 18, but most pregnant teen-agers aren't informed enough to seek prenatal care, follow a healthy diet and take vitamins. You can see why you must take the best possible care of yourself if you do carry your child.

In this case, you also must decide whether to marry or not. If you don't -- and there doesn't seem to be an enduring love here -- you could arrange an adoption. It would be very hard to do, but you would give the child a better chance at happiness and great joy to some childless couple.

Or you could keep the baby, as a single parent. This means having a child who gets sick in the night, with a fever of 104 and rising. It's having a 2-year-old throw tantrums, a 4-year-old turn sassy and an 8-year-old become such an individual, with such real fears and dreams that he or she constantly invades the privacy of your mind.

Having -- and keeping -- a baby is having a 10-year-old who's usually a delight, an 11-year-old (and a 13-year-old and a 15-year-old) who's sometimes a despair and an 18-year-old who leaves home, just when his personality is falling into place.

And through it all, having -- and keeping -- a baby is having, somehow, the money to pay for the groceries and sneakers and bus fares and day care. And wanting to do it because you know the child's needs are more important than yours (most of the time).

Having -- and keeping -- a baby isn't a 9-month adventure. It's a lifetime marathon. For many mothers, it's the greatest adventure of life, but you might not be ready to run this particular race.

This leaves abortion.

It is a much more complicated issue than extremists on either side generally admit. The same groups that accept the taking of a life in war, in capital punishment, in a terminal illness, are often dismayed by abortion, while those who advocate abortion often get outraged at the destruction of snail darters. A middle view sees abortion as a tragic solution that is sometimes necessary, although not nearly as often as it occurs.

Only you can decide, not because "it's your body," as many say, but because only you know whether, at 17, you are strong enough to give your child away or do the rearing yourself. What is wrong for one person is right for another.

To help you make the decision, read Thinking About Abortion by Beryl Lieff Benderly (Dial, $13.95). It explains the various types of abortion and where to get them, without glossing over the facts. They aren't pretty.

Although the book considers abortion for what it is -- the taking of a life -- it may also help you realize that sometimes it may be more moral to take a life than jeopardize the lifetimes of three people -- the child, the mother and the father.

If this is your choice, ask the National Abortion Federation (800-722-9100) to recommend an agency with a strong counseling service, both for now and later. Abortion (like adoption) can make you grieve for months.

The agency also will give you birth control, and with good reason. Sex is a recreational drug. Once tried, it's nearly always tried again, although a wise woman waits until the right relationship comes along and uses precautions even then. And may you be so wise next time.