This one is a tough one but I'm gonna go with ESH.

On one hand, I think I definitely agree with you that your boyfriend should respect your decisions, particularly since he started off as the smoker to start with and he's the one who pushed you to change methods until they got progressively worse (in his opinion at least). This is especially true if he is still smoking while telling you not to.

At the same time, I think that lying to him and not telling him about what you're doing is just as damaging to the relationship as what he is doing. It's sort of avoiding the problem instead of addressing it head on. I also can't tell from what you wrote whether or not you discussed your opinions on his smoking when you first started dating. If you never said anything, it's not really fair to use that against him.

At the end of the day, a discussion needs to happen. Your boyfriend needs to decide whether or not this is a breakup-worthy issue and stick to it. You need to decide, in the event that he does say it's critical to him, whether or not you're willing to change for him or not. You're totally free to do whatever you want but he's also free to have things that are dealbreakers for him, whatever his reasons might be.