Im 15 and my boyfriend and I had sex last night. It wasn't even that long of time that it lasted. Maybe less than 5 minutes. He doesn't know whether or not he came. I have an irregular period, I just got off of it about 4 days ago and I'm scared I might be pregnant. I cannot be pregnant!! I cannot tell my parents!
See the other post.
Having sex 4 days or so AFTER your period you are becoming more fertile. You'll likely ovulate in a few days. Sperm can survive about 5 days though.
It doesn't matter if it lasted 5 seconds or 5 hours. Even if he didn't ejaculate precum can contain sperm. All it takes is one.
Always use some protection - one of you at least.