Suggest Treatment For Chronic Severe Cough

I'm 29 year Male having severe cough for the last 40 days. I have taken several syrups and tablets which were of no use. From last week i'm taking Montek-LC tablet every day in evening. It's good but only temporally rest from cough not permanent..I am a regular smoker too, but drink alcohol very solemn and that also of a very little volume. plz suggest