Even if a man doesn't ejaculate, some sperm can be released before he does. So 'pulling out' doesn't work. Hang in there, and if you must be sexually active, (which you are under no obligation to do, no matter what people say!) avoid intercourse. You are most fertile mid cycle, but women can get pregnant any time during their cycle. It is OK to say no to sex, even if you have had sex with your boyfriend already. Sometimes people think that once they start they can't just say, "hey, we took a risk, now we should not do that again!" but you can.