He is Killing Me

How do I tell my boyfriend that he needs to stop smoking . He doesn’t smoke outside he smokes in the room and I told him certain times he should quit he doesn’t even take it serious why because he is addicted and can’t stop . He is driving me crazy and I can’t take breathing it up or the smell anymore , I don’t want it to ruin our relationship but if he continues I’m not going to be able to be around him all the time 😩 I don’t want to god forbid get second hand smoke. It’s been really messing with my breathing lately having me cough all crazy . What can I do 😫