Sex, blood, period?

I lost my verginity almost a week ago and I bled and it hurt so I made him stop. Then yesterday I bled a little bit, I thought it was just spotting so we had sex that day. I bled even more and it hurt worse than the first time. Today I've been having cramps and so much blood just like my period. But I'm on birth control and only on the third week so could it be my period or is something seriously wrong? I'm kinda worried, please help!