please help!

So last night my boyfriend and I had sex and I've been on Birth control for four months now. He had nutted in me and now I'm super worried that I might get pregnant, I'm only 16 so my parents will killll me if I get pregnant, do you ladies think I will be ok or should I go buy a plan b?  I take my birth control regularly in the morning besides on the weekend I take it whenever I wake up.