Has anyone ever had this happen?

i started birth control 3 weeks ago to help regulate my period. I've been off for almost 2 weeks. I just had sex at like 4am and after I went to the bathroom and I was bleeding alittle like you do when you first start. I still am bleeding little like spotting and its been like 15 hrs since we had sex. How do I know if maybe he cut the inside of me? How long will I bleed? I don't think it is my period because I got off it about a week and a half ago.

Advice please! Thanks!