Sweets, I haven't had any bleeding, but I've heard of this. You could have had a small bump on your cervix (completely normal and benign) and OH could have irritated it when you dtd. You'll get brief dark blood from that. You could have also had blood already pooled high up (maybe from implantation/a light period that didn't come all the way down) and his weewee (haha) displaced it.