My boyfriend is a smoker..

So I found out my boyfriend smokes cigerettes. He told me he quit one time but now smokes anywhere from 1 to 5 a day it just depends. He said the only way he would quit is if he was with me 24/7. Being 18 it's difficult trying to be together all the time because of work school and personal things. Idk why it hurts me so much that he continues to smoke, he said it's something he feels like he can't control but he would try to quit, but it's hard. Yesterday I found a box of Newport's with 3 cigarettes in it in his dresser and my heart kind of sank. I was thinking maybe I should write a little note and leave it in the box so when he goes to smoke again he'll see it. I thought it would be a good idea. Like every once in awhile do it, like a support system type thing. What do you guys think? Any advice?