doing it doggy style

Ok so my boyfriend and I started doing it doggy style a couple of days ago and I felt like something was coming out so I turned on the light and I was bleeding. I figured I got my period or something but then the next day I was totally fine and not bleeding. Then yesterday we did it again(doggystyle) and I started bleeding again! I'm like freaking out as to why this happened..if anyone has experienced the same thing please let me know why this happens or anyone who knows as to why you can bleed during sex..thanks ladies 💞