I did it again...

I promised my boyfriend I wouldn’t do it again because if I did he would break up with me...I suffer from severe anxiety and depression due to being emotionally/mentally and physically abused my my mums ex and he knows I struggle with everyday life but sometimes I feel like I’m not enough for him so I have these depressive episodes where I just turn into this complete different person and do/say things I wouldn’t normally. Yesterday I thought he was cheating on me because in the past he’s been a bit too...”close” with his ex or his “friends” so I worry. Anyway I was in my head and completely out of it, we had a massive argument and stopped talking for a few hours. Within those few hours I zoned out and apparently took a shower and cut...I’m scared to tell him because he means everything to me and he genuinely cares about me. He’s gotten so much better over the past year but I’m always the one who brings it up because I can’t seem to get over what he did. What should I do please help me