Worried.

Sarah • Sarah. Cats, Country & Batman. 20.
I just started birthcontrol, literally, a month ago. Before hand, I just used the "pull-out method" aka withdrawl. Never had an issue. Well, my period is three days late. The last time my boyfriend and j had sex, before yesterday, was the 24th of October. Is this just part of birthcontrol? I'm on the pill. Or should I be nervous?