Kept the covers over my head for this exact same reason. I figured I would feel it if a vampire tried to remove the blanket or sheet and I could defend myself… no real thought or planning put into how I would defeat a vampire, but at least I’d be awake. A very religious aunt told me vampires don’t exist and that it was in fact demons sent from hell that were trying to get me and all children… I was four when this was explained to me. It’s one thing to get scared because you saw a movie about a kind of monster and quite another to have an adult you’ve been told by your parents to respect explain what to her was a real monster and one of which she was convinced actually existed. I was a very light sleeper well into my teens.