What Causes Constant Cough?

I am 53 years old and suffering from cough from the past 5 years. Morning getting white flum and black (pollution like) spot in flum. After getting out white flum I am feeling normal. Again in the evening after 4.30 p.m. I am getting some cough. Sometimes feverish but not fever to thermometer. Please guide me in Homoeopathy if not allopathy.