Worried Something Is Wrong

I have been with the same guy for over 2 years now and last night we had sex and I didn't know until afterwards but during sex I was bleeding and it was a lot and it stopped like an hour after I didn't start my period and I'm not bleeding anymore this has never happened before and I have PCOS we are TTC and I don't know why this happened or what could have caused it and I'm worried that something might be wrong and I don't know what's going on ... Any advice!?!