I've just found some dried blood on my bed sheets whilst changing them. I don't know where it came from but am paranoid that it was from the last time I had sex with my Boyfriend. None of us saw any blood (despite this patch being fairly large) and I didn't have any blood inside me after. For this reason is it unlikely it'd be from sex? Surely if I had bled I'd have seen some blood, found some inside me or he would've had some on his penis?