Thanks for posting your query.
There could be possibilities of lower respiratory tract
infection and heart disease
Smoking predisposes to both of these disease.
Presence of bronchitis
also increases the possibilities of underlying pneumonia
You should again consult to your treating doctor/ internal medicine specialist and should go for thorough check up.
You should also go for chest x ray and electrocardiogram to rule out above mentioned diseases.
You should quit smoking for future better life.
Dr. Mayank Bhargava