An an ex radiographer, from my memory, and the remaining textboks I still have, you would have to had smoked quite a lot for the effects to show up on a CXR - apart from the obvious occasional malignancy, - which we hope you're clear of - the general appearance of a smokers CXR is greater definition of the airways within the lung, (Generally looks 'whiter')as they become clogged with tar etc. but it takes more than the occasional roll up to get this far. However, in the case of Emphysema, when they are excessively full of air. (A' la Linda Evangelista) the lungs look very dark.
What exactly are you concerned about? Have you been telling porkie pies to the quack, and are worried you'll get found out? In this case I would advocate cutting down your cigarette intake, allied to total honesty.
In any case I would advocate cutting down on your cigarette intake.