What Causes Bleeding After Sex?

Hi,
I had my period this month on the 13th (there about) and finished on the 19th. I had sex on the 22nd... it was a bit more painful than usual. It was protected. I usually never know when my partner cums into me but when we were done, he asked if i was still bleeding or if he came into me. I wasn't sure (maybe the condom broke) so I used my usual contraceptive all the same. On the 28th, I started bleeding again, first lightly, then it started coming up fuller. Today the 31st, it's lighter. No cramps... I usually have cramps when I'm on my period. I'm very much terrified.