Should I tell my best friend that I cut myself?

Hey, I (17F) have been struggling with my mental health for years. I can't get help, because my mother thinks mental illnesses don't exist and if she ever found out about me self harming she would probably kick me out of the house (she thinks that people who self harm are (by her words) just a bunch of pathetic idiots). Of course, as soon as I will be able to move out of my house (so, hopefully in a year) I will seek professional help.

I was bullied really bad in middle school (the bullying was the main reason I started harming myself). But, since I went to highschool everything changed. My school is quite far away from my home, so I live with my roommate. I have two very close friends (so close that I could easily call both of them my best friends), one them is my roommate, let's call her A (17F) and the other one is M (17M). I don't really think I am able to talk to A about all this, because she always saw me as strong and I can't bring myself to be that vulnerable about her.

Lately, my mental state declined really badly. I won't go in details, but my home life is very not great. The situation in my home and school has caused me to feel extremely bad for last few weeks.

In highschool my social life has become good and for the first time I got a solid group of friends, who really seem to enjoy my company. I was feeling so much better last few years and almost stopped harming myself.

But lately I just can't take it anymore and feel worser than ever.

M knows that I've been feeling bad lately and he's really supporting, but he doesn't know how bad it's gotten. He suggested that I'd talk to school counselor and I will be doing that, but I wonder if I should tell M that I am cutting myself. I really don't want to burden him or traumadump on him. But if the same was happening to him, I would want him to talk to me if he needed it. Still, I am afraid of being a burden to him. What should I do?

Also, I really apologize if my grammar is awful. English is not my first language.