Thanks for posting your query.
Although you have stopped smoking
but if you have already developed chronic bronchitis
then you have to take other bronchodilator
therapy apart from inhalers.
You should consult with internal medicine specialist & chest physician and should go for thorough examination.
Exact cause can be detected only by clinical examination.
You should go for sputum culture
& sensitivity for detection of microorganisms and appropriate antibiotics.
You should also take aminophyllines along with mucolytics.
Hope that helps.
Dr. Mayank Bhargava