Bleeding after sex?...

Li
It doesn't happen often...
So, don't think I'm bleeding EVERYTIME me & my SO have sex. 
It's only happened a handful of times. It's always after rougher sex or when we do it "doggy style" (they need a different term for that). 
Well, last night we did that and I bled a little bit, which I figured out by him coming back into the bedroom showing me the little bit of blood he had on his man part. 
Sorry for the TMI. 
I got on Google last night, big mistake, and I self diagnosed myself. I seriously convinced myself last night I'm dying. So, SOMEONE PLEASE TELL ME THAT ITS NORMAL.