Every time I get sick the usual symptoms of headache, sore throat, weakness, etc. go away after a day or two, but I have this lingering cough that more often than not lasts an entire month. I have no other symptoms, feel fine, and am able to go about my day without being hindered, but my chest is full of phlegm and the constant coughing bothers those around me. What is it that causes this to happen to me when others get over a sickness in a day or two? What can I do to speed my recovery?