Fiancé won't stop smoking

So my fiancé is pretty much addicted to smoking weed..I don't have a problem with weed or judge anyone who smokes it, it's just not my thing. I never yell at him for it but I've asked him nicely for the last 5 years to maybe not smoke every single night. I hate having sex when he's high because he can barely stay hard and literally stops in the middle to grab water or sometimes just gets too tired. We're currently ttc so it's a little hard to do that when he can't perform sometimes. His response is always 'I like it and I want to smoke so I'm going to' even though I've told him how much it bothers me. Ive cried, sat him down, almost anything and he'll maybe stop for a day or two and go right back to smoking every night. Ive also seen him pass out and even split his eye open from being so high. What should I do? I'm not going to break up with him over it but I really want to be heard and for him to not do it every single night. Please help :( sorry for the long post!