Birth control can do mysterious things and sometimes change your mensturation cycle. However, I am assuming you are still young. Bleeding is common if you were a virgin, especially if it was "rough".
However bleeding for more than a day after your first time having sex, is not healthy. You do not know that it is mensturation either. I would advise you to consult your family MD or gynecologist.
i had the same thing happen to me. i freaked out too but stay calm. sometimes if you panic like tha tyour hormones just up and can stall out your normal period. i eventually got my period 10 days late and it only lasted a day or two and was very light.
birth control can alter ur periods and cause irregular bleeding.