What Causes Excessive Coughing After Exercise?

I have had a cough for the last 6 - 8 weeks. And lately after hard training sessions iv found it hard to take a deep breath. How ever it is now hard to take deep breaths all the time. It is like a tightness sensation when I try. When I stop running after training I cough a lot to the point of nearly getting sick. What do u think it is??