Hello
I appreciate your concern
Cough for 3 years duration with history of smoking is a matter of concern
Thus could be related to chronic
bronchitis, COPD or
tuberculosis and a lung cancer
Another possibility is
acid reflux.
Here, I would like to know if you have lost any weight?
ever you have coughed out blood?
Your complete medical history like
diabetes or any other metabolic disease
I would advise you to consult a chest physician for physical examination and a battery of tests like blood for
hemoglobin, CBC, ESR sputum test and pulmonary function test
Meanwhile you can do deep breathing exercises and Steam inhalation
You should quit smoking now
Thanks for your question please feel free to ask for more assistance I will be happy to help you
Best wishes