Thanks for your question on Healthcare Magic.
I can understand your concern.
No, this is not due to muscle build up.
Wheezing on deep breathing is due to
bronchospasm.
Since you are active smoker, possibility of
bronchitis is more for your bronchospasm and wheezing.
Cigarette smoke causes irritation and inflammation of the airways. These lead to bronchospasm and wheezing.
So quit smoking as soon as possible.
Consult pulmonologist and get done clinical examination of respiratory system and PFT (pulmonary function test).
PFT will not only diagnose bronchitis but it will also tell you about severity of the disease.
You may need inhaled
bronchodilator and inhaled
corticosteroids (ICS) on the basis of severity of bronchitis.
So if don't start treatment at this moment, you will develop severe bronchitis in later life.
Hope I have solved your query. I will be happy to help you further. Wish you good health. Thanks.