Bleeding after sex?!!

What does it mean when you have vaginal bleeding after sex? Me and my fiancée were just getting done having some pretty great sex and ended up falling asleep afterward. 20 minutes later I wake up and feel a wetness between my thighs I'm thinking I'm just horny again because that usually happens when we fall asleep and he's pressed against me. It's like a waterfall down there lol but it wasn't that it was actually blood and a lot of it as if my period was just starting. It stopped not too long after but now it's been a couple days and I'm really scared to have sex again my fiancée knows about what happened and keeps telling me it's normal. He would know because he's had more sexual partners than me. He's the only man I've ever been with. Anyways I know this is long but I think I should go to the doctor. What about you? Anyone else experience this?W