Gosh, no one should have to live that...you must put a stop to it immediately.
I would do four things:
1)I would change all the locks, or if it easier, add a new deadbolt above each old lock with a new different key.
2I would absolutely contact him BEFORE he gets back and finds the locks have been changed....you don't want him showing up in the middle of the night learning this for the first time.
3)I would notify the police just in case....at least find out who exactly you would call if things escalated.
Let them know you do not want him living in your house and you want to exercise your rights.....maybe get a social agency involved.
4)KIck that husband of yours in the @$$ and tell him he should be protecting you!