Boyfriend problems

My boyfriend has depression and anxiety and he's another personality and wants to start cutting agian. We are good and bad his moments go up and down and the bad are coming all the time he has help for doctors and therapist and I'm going crazy cause he wants me to leave him or he try's to say he did hurt me but he hasn't. And I tell him no and then shit blows up and it gets better. We went out and had a great night last night and this morning hes pissy. He gets worse when we don't see each other for a week or 2 I try o make him happy and it works when I'm around only but after that he's goes down. I don't know I can't be there all the time cause he works slit and I'm at school. I really need him to improve cause my mum is going to force me to break up with him and I can't cause if I do he'll kill himself or destroy and break down     I love him and i don't know what to do or say anymore