Quit Smoking

My son is a month old today, and the day we found out I was pregnant, my fiancé promised he would quit smoking before the baby came. I told him I did not want it around our baby and he agreed with me. He waited until the last minute to finally "quit". When I say last minute I mean to the day I went into labor. I gave him some skepticism leading up to the birth of our son and he just told me to trust him that he would quit. Here we are a month after the birth and I noticed every time he gets home he's chewing gum which he doesn't do on a regular basis, and he smelled like febreeze. I'm no dummy and I suspected that he snuck a cigarette. I understand it's a difficult habit to quit, but I gave him 9 months to figure it out and he promised he would. Tonight I had to get something out of his car and when I opened the drivers side door there was a pack of cigarettes and a bottle of febreeze! It's really unlike him to try to hide something from me and I feel a little betrayed. I'm trying not to make a big deal out of it, but it hurts me. He doesn't know that I know. How should I approach this with him? He was supposed to quit for our son because he didn't want to be a smoking daddy.