What should I do?

I’ve been with my boyfriend for a while now and we are long distance and I just feel like I should end this relationship for issues that we have. The main issue however, is he occasionally drinks cough syrup . I’ve been with a guy that has done drugs before ( no I don’t mean weed) and I honestly can’t be with someone like that. I talked to him a couple of times on the phone after he drinks it and it so unattractive and frustrating. Long story short we do plan on moving in together in a couple months and I honestly really don’t know what to do. He lives out of state for work so once I move there I’m alone, and if things don’t go right I’m putting myself in a bad position. Advice ?