Congrats for stopping smoking
, though its quite early to wish you.
The problem that you have stated could be mostly due to the infection in your lungs. The smoking for 25 years might have seriously damaged your respiratory immune system making you prone for infection. May be a course of antibiotics with good expectorant and steam inhalation could do good to you. If you find time, do X-ray your lungs once.
Hope i am able to solve your queries.