What should I do....

so I have been trying to tell my boyfriend of 5 years that his mom takes my things without asking me and always ttys to find some lame excuse as to how she doesn't mean it like that, how she's a really good person and likes me.... we've stayed with her the whole 5 years and I have been going through this almost 3 years now. I don't care how small it may seem to others but my things are my things and if you don't ask me for it you have no business touching anything of mine. my tissue, my soaps, lotions, socks, shoes, hair products, combs , brushes perfumes. I have all my things in 1 room and most of the time hidden in a draw or cabinet and she would actually go through the cabinet or drawer to get what she wants.... that is in no way ok.... and he does not want to admit it.... him and I were staying in a hotel for a few weeks after Harvey and my mom and brother came to spend a few days with us he was telling me how he would fight my mom or brother if anything came up missing what the difference.......he will not say anything to his mom about it and I told him if something else is touched I'm saying something and we're gonna have some issues.he refuses to move out so I'm literally just fed up with everything! the entire 5 years i have not had not 1 dis agreement with hos mom even despute her gaking my things.... i barely even talk to her around the house...... yes she has helped me by letting me her son and my 1 year old stay in her house for so long. she gives us rides almost every where. but that does not cover her touching my personal belongings..... so ladies what should I do in this situation?