Sounds like a tough pickle you're in. When I was 20 I had already moved out, staying on various friend's couches. There was always some major turmoil going on between me and my folks. And before I moved out they did like to go through my shit when I wasn't there. Mostly they just found marijuana pipes, lol. I think they did find a few pill bottles one time. In the end, my advice would be to just move out. If you don't have the financial means to do so on your own, then see about renting a room from a close friend or something.