I do not agree with Southern Belle .Your boyfriend is entitled to ask that you quit smoking. Your 'right' to smoke ends at his the tip of his nose. This is not about your 'right' that you have to do as you please, and to try to make him the bad guy for trying to 'tell you what to do ' is really defiant adolescent thinking.
It comes down to this -you have to decide what you want most.Either you want to continue smoking OR you want to stay in a relationship with your boyfriend! Your choice !