Thanks for writing your query.
It will be helpful if you give more information on :-
1. History of smoking.
2. Location of chest pain
After reading your post, I would like to suggest that you should get following investigations done :-
1. Sputum examination(Culture/Sensitivity).
2. Complete Blood Count(CBC).
5. Chest X-Ray(PA view).
You can add mucolytic agents like Bromhexine
, after discussing with your doctor. It will help to liquify the phlegm and help in expelling it out more easily.
Medical management can be planned after clinically examining you and according to the reports of the investigations mentioned above.
I hope this is helpful to you.