What to do after unprotected sex, if you don't want to get pregnant
The first thing Don't do it again
The next thing you want to do is look into Emergency Contraceptive. You can get more info at that node, but if used with in 72 hours or so after the sex, it can reduce the chance of pregnancy by up to 70%. Call 888-NOT2-LAT(E) or look in the yellow pages for Planned Parenthood.
Get tested for STDs: look in the yellow pages for a local anonymous clinic or talk to your doctor.
After two weeks you can get a pregnancy test. Do so. If it turns up positive, you should take another, just in case, and start to think about adoption and abortion. You might also look into RU-486, an abortion pill, newly legalized in the USA.You probably aren't mature enough to take care of a kid, really very few people are.
Get condoms and the pill for next time.