28F, 31M.Why am I still stuck in a relationship that is destroying me?

Lately, he's been smoking marijuana every day. From morning to night. If it's not alcohol, it's marijuana. I'm really fed up with it all. I feel alone in everything. Nothing interests him, even though at the beginning of our relationship he talked about self-development, healthy eating, and meditation. He doesn't do any of these things. When he gets home from work, he plays games and watches YouTube. He feeds his mind on sweets and fast food, and drinks a lot of caffeine. This is my first serious relationship. I'm 28, and he's 31. He has a child from a previous relationship, whom he thinks about a lot, but he doesn't contact him at all. For the first two years of our relationship, he constantly talked about his ex, and he treated me like air. He also watched a lot of porn, which is why we practically didn't have sex. All this time, I wondered what was wrong with me, what I was doing wrong. Recently, things have started to improve between us, but I still have unresolved emotions related to the beginning of our relationship, and I occasionally get hysterical. I should also add that at 28, he was involved with a 17-year-old girl. That also pushes me away from him. He has debts that he doesn't repay either. He's the first person I've ever loved, but it's becoming increasingly difficult to function with all this baggage on my back. He's been trying for several months now, and we're very close. He's done with porn. But whenever there's a problem, he always runs away and refuses to take responsibility. Could I ask for your advice?