Without examination and proper evaluation whatever information I'm providing here is at best an educated guess. You should see your doctor if the symptoms persists.
It sounds like you are having hypersensitive airways after flu
. Also possible is infection of the lungs and bronchitis
as you are continuing to smoke. With past history of double malignancy and in case of doubt if the doctor doesn't think its because of infection, getting a plain Chest xray is not a bad idea either.