You go out as soon as you can get, get a pregnancy test (they can be used as soon as you miss your period, or at least tne days after the incident when you might have gotten pregnant), take it, and . . .
If you ARE pregnant, we have advice on talking to parents here: http://www.scarleteen.com/forum/Forum10/HTML/000259.html
If you are NOT pregnant, you go out and get some good quality condoms and lube, and use them EVERY time you have sex, so you don't have to worry so much in the future, or else you choose to remain celibate until you're able to deal with the risk of pregnancy.
Milke, SSBD, RATS
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