Relationship

My boyfriend and I have been together for 1 1/2 years. When we started dating he stopped smoking. He started smoking again... I hate it, and he knows it, but he told me he’s not quitting. He won’t even try. I don’t know what to do. I love him and. Want to marry him in the near future, but the fact that he started smoking again makes me feel like a horrible gf for not being able to be ok with it. And he won’t see my side of this. Like the fact that it can kill him, sooner or later and I want to have a family with him one day, and don’t want to take the chance of losing him, because of smoking and it one day killing him. Help, I don’t know what to do.......