After doing cardio exercise i get bad cough and spit very dark mucus and sometimes very little blood (pinch of blood) as well. the blood comes only once. This continues for at least 15-20 mins after doing cardio. The coughs are very deep. More deep is the cough more black mucus comes out and sometimes i get very bad pinching pain in my chest (just middle of chest). This is happening from last 3 months. I smoke 4-5 ciggs a day from last 7 years. Recently i got medical chk up. My ECG and Chest Xray are normal. Please suggest ..HELP!!!