I used to live with a boyfriend like this. We'd got together when we were 18. He smoked cannabis very, very occasionally at the start but about 3 years into our relationship it became a daily habit. I think it was because he'd just finished university and was struggling to find work. He became so boring. He wouldn't go anywhere or do anything with me because it would get in the way of his smoking. He was dull, paranoid and lazy.
He was suddenly no support to me. If I needed him he could never help. He missed my graduation ceremony (which he knew I'd really been dreading and didn't even want to go to) by pretending to be ill that day. I knew he wasn't ill, it was just that he wanted to stay at home and smoke.
I got myself a job and started making friends at work but he didn't want to know. He wouldn't meet my work friends because he thought they'd think he was stupid. If we did meet up then he'd be very sulky and barely talk to anyone. He'd always been the more sociable one of the two of us and it was a real shock. He tried to spoil my work for me by doing things like stopping me from sleeping or turning my alarm off while I was asleep to make me late for work. He'd phone me at work ranting about things and then in the evenings he'd sit staring into space.
I found it really difficult to accept how much he'd changed. It was weird seeing that other people didn't like him when he'd always been popular.
After 4.5 years together I managed to tell him it was over but it was hard as I felt like I was abandoning him. He said I was leaving because he didn't have money and now I had my graduate job I was only interested in people with money etc. It was all nonsense. I was leaving because I needed a partner. I was lucky that we weren't married and didn't have children but it was still difficult to make the break. I thought I'd never meet anyone new. I was very young but we'd done a lot of growing up together (well, I had) and he was a very important person in my life. It would have been harder to leave with children but I think I could have been more motivated in those circumstances as it would be awful for children to grow up thinking that behaving like his was normal!
We rented a flat together, which of course I paid the most for. He refused to leave but I managed to get our contract terminated early. This meant that he had to move back in with his parents 150 miles away. He was very upset about this and when his Dad came to pick him up I felt terrible. I can still picture him being driven off.
We kept in touch for about a year after I left (him phoning me at work threatening suicide etc.) and then he found someone who liked drugs as much as him and he told me he never wanted to hear from me again.
This is all about 20 years ago now! I found someone else very quickly. Lovely, reliable man with no interest in drugs. We've built a good life together and have 2 children.
I've recently heard that my ex now has severe mental health problems. I think he was depressed when he started to smoke daily and was using the cannabis to cope but it would only have made things much worse. Me staying wouldn't have saved him from this. He could have seen me leaving as some sort of wake up call and got some help then but he chose not to and moved on to much harder drugs, including heroin. I've heard he now has to have live in supported housing as he can't cope on his own. The new girlfriend is long gone which didn't surprise me as apparently they used to argue a lot over drugs (as in, stealing drugs from each other etc.).
I'm so glad I got out. You sound lovely and I'm sure you would be much happier if you got out of this relationship. 