Bleeding During Sex??

So I had sex this evening with my boyfriend. He wasn't wearing a condom, but before he came, he pulled out and just finished all over my stomach. After that we realized there was blood on his dick and all over me. We were doing it pretty rough, but no more so than usual, and I've never bled during sex before. My period is due sometime next week, so is it probably related to that? Or is something wrong??