What could be up with my boyfriend?

Obviously this isn't the place to diagnose him but wondering if anyone with experiences have any ideas of what he could be dealing with? Maybe it sounds familiar? He won't go to a doctor so no proper diagnosis.

He's a very negative person. Like definitely glass half empty kind of guy. But also everything is the end of the world. Anything from he has no friends so whats the point in anything, to when he cooks dinner and starts swearing madly because he dropped an onion and thats it no point carrying on! Like he is very drastic in his thinking. But only negatively.

He is rarely happy and when he is its like subtle happy. Generally not like oh this is amazing! But more like well this isn't too bad (while smiling so you can tell he likes it a lot). He is never excited, about anything.

He also has no interest in anything. Not even sex even though that was a huge part of our relationship. Trying to choose what to watch on netflix nothing is good enough. Choosing what to eat, everything is rubbish. Has a day off work, but nothing is interesting enough to do so he just plays xbox or sleeps. Like he never wants to go out and do things whether it just be a walk in the sun or bowling.

The sex thing, well he masturbates every day but he never wants sex. Like its too much effort? When we do he doesn't get excited or act like he is loving life like he used to. Like it used to be so fun and experimental just rolling around naked.

He also smokes weed every day. If I do manage to persuade him to leave the house to do something he usually smokes a bit beforehand even tho once we are out he then doesn't want to speak to anyone or order food etc because people will notice he is high. It's like nothing is fun or interesting unless he smokes, but even then it still isn't fun.

My thoughts is depression? But is there anything I can do to help him or does he definitely need to see a doctor? He doesn't do tasks, like calling a doctor etc he will just never do. I had to call and drag him to a dentist after months of pain. But doing the same with a doctor feels too pushy?