Right so you've waited three nights to post about this, mate. Three. Nights. Bold strategy.
Jokes aside though this is actually one of the more unsettling setups I've read on here in a while, mainly because of that detail about it moving. Static breathing under the bed is creepy enough, could be pipes, could be the house settling, your own echo bouncing weird off the floor. But moving is a different thing entirely and I can't explain that away as easily as I'd like to.
Did you get any photos or were you too busy absolutely legging it out of the room? Asking for a mate (the mate is me, I also want to know).