bleeding in between period....

Tee

Hi everyone, me and my partner had sex today, he came inside me, but as I was cleaning up afterwards we noticed blood mixed in with the cum.... He thought I had come on but I'm not due on for another week or so. The only other time this had happened after sex was a couple years ago when I found out I was pregnant weeks later, but that led to a miscarriage. Has this ever happened to anyone before.?