That's interesting. Do you think it's largely because of congestion, that you can't seem to get enough air?
And are you strictly a nose breather? (I'm guessing you are, since you were fitted for those). I know some use nose spray, forget the name, I know someone will mention it here. If you found yourself breathing through your mouth some, I would say try a full face mask. What's your prescribed pressure? Did you oxygen levels improve after starting cpap? Did they test you for that after using your machine for awhile?
Look, I know kicking smoking is hard, and I would never tell you to stop. Both my parents smoked (me and my brother never did), but I saw how hard it is. They say smoking is probably one of the strongest addictions there is. People don't always realize that, they think it should be easy. It's not. So I understand.
Keep in touch, and maybe we can suggest some things to help.