Period&Pill

So I've been taking the pill for a few months now. When I reached the placebo the past few times, I've gotten my period on the Wednesday (I start new pills on Sunday's). Today I was supposed to get it but it shows no sign of it. On Friday, my boyfriend and I were having sex unprotected and he didn't pull out fast enough. That's what the pills are for right? I'm really nervous that I could be pregnant. Maybe my nerves are preventing it from coming but I just really need some reassurance.