You have taken the right decision to
quit smoking, that’s the first step, now follow it up and don’t give in to
smoking.
The lungs age with smoking as in comparison to the person’s age. If you stop smoking at this point, the lungs are not damaged any further, though the damage that has already been done cannot be reversed. So, the breathlessness could be due to compromised lung functions. You can discuss with your doctor about nicotine replacement products or other medications.