How do I approach my fiance about his hidden smoking habit?

My fiance was a smoker when I met him. He quit shortly after we started seriously dating, somewhat for me but mostly so he would not be addicted to something and require it to feel good. During our first year he started again and hid it, later telling me about it. It caused a huge argument. He quit again and lasted until we moved in together. He moved from another state to be with me and was stressed. Then he started again. I caught and confronted him, leading to another huge fight. I feel as though there was another time he smoked, but quit on his own in between these times, but I can’t remember for sure. And now he is smoking again. I can smell it and I found a receipt lying on the floor dated 3 days ago for a pack of Dorel Gold.
For the past week and a half I have been wondering whether to confront him or let him come to me. I spoke with his mother and a few of my friends for advice… I get mixed answers. The best so far I have heard is just to let him know that I know. If he is hiding it, he is probably upset about it.
I just want some advice on how to handle this situation. I don’t like smoking myself, and I prefer to be with a nonsmoker, but I truly love who he is and being with him. I believe he is stronger than this, but I feel like I am not giving him something he needs if he is turning to this bad habit again. I am hurt that he would hide this from me… again.
What do you guys think? Thank you in advance for any advice on the matter. This has been upsetting me for too many days but I feel too unable and unknowledgable to bring this up to him. Plus, I don’t want another nasty fight about this. I’m dreading the nicotine withdrawal again. Thank you.