Re: is this due to smoking?
I think that you may want to talk to your doctor about this. I don't think anyone is really qualified to answer this question and trying to diagnose someone through the internet isn't all that reliable anyway.
I will tell you this. Smoking puts a strain on the heart that is about the same as if you weighed an extra 75 to 100 pounds.
Every cigarette you smoke causes the heart rate to increase by about 20 beats more a minute. The cycle of smoking is viscious, because it causes the heart to work harder, so the heart needs more oxygen to do this. The problem is that the carbon monoxide from the cigarette smoke basically poisons the blood's ability to carry oxygen. This in turn makes the heart have to work harder to get more blood to it to get more oxygen to it.
A lot of people believe smokers usually die from cancer. The truth is, that more smokers die from circulatory conditions, such as heart diesease than from cancer.
My advice is to quit smoking. When I smoked I git very easily winded and used to ahve a burning sensation in my lungs when I did physical activities. Today it is nothing like that. I have a lot more stamina. I breathe much easier and that burning sensation is gone.