A lock on the bedroom door, too. Even one of those hook and eye types would work, they are inexpensive at the hardware store. He should never even be in your room, let alone have access to your clothes.
Do you have any trustworthy relative you can move in with, such as an aunt or grandma? Your mom is clearly not able to say no to this guy, and you should not be there for him to prey on. In my book, she is not doing enough to protect you. But if you say she is doing all she can, then it's up to other people who love you to step in and help you.
Was he convicted of any sex crimes in the past? What does your mom say about all of this? Is your dad in the picture? If so have you thought about moving in with him?
Tell your dad. Make a police report by calling it in. Just enough to harass your uncle. But when there is a will there is a way. While you shouldn't have to be on lock down, take your clothes INTO the bathroom. Use a robe and go into the closet to change or grab your clothes and go back to the bathroom.
When you say it didn't start up again when he moved back in, what do you mean?
PS, you are almost a legal adult. What is your plan for the end of high school?