Any reasons why this would happen?

Emma

So me and my bf have sex regularly like anyone else but I’ve never bled from it. We bd tonight and then went to bed. Later I couldn’t sleep and was still in the mood so I decided to do it myself while he was asleep. Afterwords I went to the bathroom and when I wiped I saw spots of blood. Any idea on why I would have bled hours later but not after we had sex?