I think that cutting is the only way to calm down

Hi everyone! Recently, I lied to my best (and only friend) at school. I did it to seem better so we can proceed our relationships. He always supported me, helped me an so on. On day, he had some “vital problem” so he started ignoring me, I felt really bad as didn’t know whether it was me who started all this. I texted my friend from the other school and she told me what to do. As it appeared, just after answering me, she told everything to my friend (the one who is ignoring me) and he was disappointed. The next day he asked whether I texted her or not. I didn’t know what to say, he said it with such pressure! I lied that I didn’t and he furiously went back to his room (we are living on campus but not in the same room). Then, I said that I was extremely sorry about the situation. He answered that he is not going to listen to my problems anymore unless I trust him fully. I started to be as open as I can, I even do his homework late at night so he might appreciate it and talk to me just like it was before. I cut myself before but he took the knife, blades, pills and so on. What should I do? I want to punish myself for that? Guys, can you help me!!! He is 16, I am 14