First of all, you DO need to go to the Dr.
But I wouldn't jump to any conclusions. It's probably GERD
(Reflux Disease) which would be exacerbated by the smoking
by the way. Reflux doesn't have to be just after eating. My bet is that, whatever it is.. it's probably related to the upper gastro-intestinal track and most likely easily fixed.
HOWEVER: GERD that goes without treatment is the leading cause of esophageal cancer, which is deadly and with the smoking, you're at even a higher risk. So, the first thought is still an important one... go see your Doctor ;-)
I doubt it's pleurisy
... Pleuratic traumas are usually sharper pains and are persistent, not "come and go." Also, shortness of breath
is also associated with pleurisy.