Hello, I Have A Cough For About Six Weeks Now.

Hello, I have a cough for about six weeks now. I do not/have not felt sick at all--except that it tires me out coughing. sometimes it is so hard to catch my breath in between coughs that it scares me a little. I am 57 yoa 5'10" 234 pounds. I have high blood pressure (no medications) and have had high cholesterol (no medications) and my family doctor has been comfortable without the meds because I am very active (I have run six 1/2 marathons this year) and workout every day. The cough is irritating. What could I do to get rid of it?