I am a lung cancer servivor of 15 years I have had bronchitus since mid july I have had a chest xray and a cat scan and my lungs are fine my cancer treatment was surgery to remove top lobe of left lung and 6 and a half weeks of radiiation?
First of all. Congratulations on your survival and i know you stopped smoking. If teh simple imaging of cxr and ct are negative, and you still cough, i would get pft's, including abg and dlco. I'd see a pulmonary doctor and make sure a bronchoscopy was not indicated or a pet scan. Highly unlikely to be related to your old disease or treatment.
Good news. It sounds as if you have a bronchitis. Because it has lasted this long. You should see your doctor.