Is this problem permanent or is it recent after a flu?Do you have any history of allergies like nose allergy or asthma? Do you have nose problems like adenoids or septum deviation that causes chronic nose obstruction? Do you have repeated sinus pain and infection?Do you work or live in a humid setting or are you exposed to chemicals at your work place?
 Answering these questions can help a doctor tell why you are having cough and then  tell you what to do.