Get this sh*tload out of my houseeee!!!!?

You are right in that he shouldn't be there. However you are still just a kid and since you don't pay the bills, you don't make the rules. Talk to your mom, tell her how uncomfortable him being there makes you. Is your dad there? If so , talk to him. If he is not there, but part of your life, talk to him. If they won't make him leave, ask for a key lock for your bathroom because it is private and it creeps you out that he is in there. I hope they listen and get rid of him. It sucks that you have to put up with this.