Actually, yes, it is related to smoking. It is because smoking permanently damages the breathing sacs in your lungs called alveoli. Thus, the damaged cells lose their ability to recoil, and your lungs kind of end up inflating. The diaphram works to help expand your lungs to bring in air, but now it also has to work extra, extra hard to make sure your lungs and your body gets rid of the CO2 that your body produces. Overtime, it gets tired and worn out, because the poor diaphram is not cut out for that type of thing. So basically, when you smoke, your alveoli is damaged so they lose their elasticity, and they are inflated technicall. And so, your diaphram has to work harder to make sure you still get rid of the carbon dioxide. Your diaphram gets super tired and there you: that's where and why the pain is there.
I unfortunately do not know of anyone who speacialize in this. I do hope you know how very, VERY bad smoking is, for yourself, for everyone around you, and for the environment. You are a part of the cause of global warming. You are a part of the cause of many sicknesses and diseases. You are a part of the cause of many deaths. You are a part of......okay, you get the idea. Good luck, and hope you can get out of smoking! =)
P.s. go see a therapist!
While I don't think it is smoke related, it is however something that you must look into.
It is important to get the right diagnosis but I hope that you will listen to your body and quit the bad habits before they really become an issue.
Hope you feel better soon.
Kathy Jo