I [22/F] broke up with him [29/M] and he has started doing drugs.. again. He says it's my fault and I feel really bad.

We were together for almost 4 years and shared everything. We were really in love, with same interests and a similar way of living, totally focused on our relationship. I've always kept in touch with my friends, so I had both him and them, but he didn't. He only hanged out with me and sometimes with my friends, but he'd rather have stayed home playing videogames. I knew that he used drugs in past, but he stopped since we started dating. He smoked weed sometimes but i've never seen it as a problem.

I started to have issues with him our last year together. He was really lazy and it began to be a problem. He never finished high school and didn't even apply to find a job. I had to give his resume in his place. He refused all job offers saying they weren't paid enough. He would never went out for a dinner or something like that and the excuse was that he couldn't spend extra money, but at the same time he spent a lot of them in e-cigarettes and stuff. But it was still ok to me. I couldn't deal with it anymore when he was disappearing for hours to play a mmo. I spoke to him about his absence in my life but he said I was only bored, that it was a though time for him (I had health and college problems in those months) and didn't know what to say, so it was pointless to text me etc.

I'll sum up our breakup. We fought a lot. He was absent and stressed, he always picked on me and got really possessive after I told him a friend of mine shared his feelings with me. I couldn't use my mobile to chat without being watched, he broke into my house to control my stuff and messaged my closest friends saying nasty things. I left him cause I realized that I had lost the perception of reality, and still now I have a tendency to justify him. I can't believe we changed so much. Btw I feel really bad cause after we broke up, he attacked me saying I destroyed him, that because of me he's doing drugs again and he often get drunk. He told me it's my all fault and stuff like that. He also said i'm an easy girl and offensive things. I know it's not all my fault but I feel bad anyway, I've seen his profile pic on a social and seems devastated. I don't know what to do to feel better about it, I wish I was less sensitive.

tl;dr: my ex boyfriend says it's all my fault if we broke up, he has started doing drugs again (he stopped when we met) and attacks me cause I have left him.