My boyfriend is turning into a pothead and I don't know what to do?

Smallorange
I know smoking is common, and I have had no problem with it before. I've had friends who were very into it, but it wasn't until April that I actually tried it- with him, of course. He has tried it a couple of times before. I never had enough motivation to do it, and I really only do it now because he gets so excited about it.
We have been together for a year and a half now, and I am living with him and his family over the summer as it is a long distance relationship. In the beginning of summer we did it when his family was away, but then it slowly progressed to the point where it was every night. I noticed he slowly starting acquiring more and more things for weed. I expressed my concern for him that he is getting too attached to smoking and that I am worried he will lose motivation to do things. He lives in a town where there are a lot of drug users that are happy being just above poverty. He told me to stop worrying about it because he won't end up like that. He's already stopped going to the gym though.
I shoved it in the back of my mind and continued. I only smoke with him because it gets him so happy and I also live with him. I left to go see family for 6 days, however, and, while I was happy not to smoke, he continued to smoke while I was away. I could tell when he was too because he would give extremely slow replies. When I returned I told him if he continues to be like this during the school year, when we are apart, then I will break up with him. Again, he denied that happening. At that point, he hadn't had a day where he didn't smoke in two months. I told him that and he said he will stop for a couple days
But, the next day he persuaded me to smoke and now he hasn't had a sober day in almost 3 months. He bought dabs and even more stuff to smoke with. He left for a week to be a camp counselor and said he couldn't smoke but he had almost a quad he took with him.

Am I wrong for disliking it? How could I get my point across even more?
My boyfriend is turning into a pothead and I don't know what to do?
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