I am looking at your problem from a different angle here and whatever I post I mean to be respectful to both you and your Mother.
Communication strikes me as the problem. You are an adult with a 5 year old and your still a child under your Mother's roof. I would guess that is how the two of you are looking at this problem.
I am a great believer in staying in the moment which I learned in therapy. Making ourself miserable is how we tend to spend a lot of time in the past or the future. We spend much time thinking about what was and what could have been. And we spend much time projecting into the future and wondering about what may happen.
I wish you the best and take care of you .
This way of thinking is indeed a great way to make much of your life a lot more miserable and limited than necessary. The key to solving this problem is of course to live as much as you can in the only moment that you ever really live in and control. This moment right now. The moment that is all there ever was and - probably - will be.
But how can you step away from the thought loops that whirl back and forth through your memories and fantasies?
How do you actually return to the present moment?
Focus on what’s right in front of you,
push all other thoughts out of your mind.
Try to be assertive with your Mom, think of putting a lock on you bedroom door as you do have a right to your privacy. I am not sure how your living arrangements are set up as this may not work unless you have a room all to yourself.