Nagging cough

Patient: I have a cough that comes and goes, but can be pretty bad at time. Drinking water lessens it, seems my body is secreting extra mucous. I do not ge a sore throat or headache from coughing so much. My doctor can find no reason for the cough. I have had people ask me if I am trying to get over soemthing. I would appreciate an ideas you have.I am tired of coughing.