any type of cardio-activity makes me out of breath, to the point that i must sit down. i can walk several level miles without losing my breath. it's only when I bend over or carry something heavy. i have recently been given a clean bill of health by my heart doctor (i had a triple bypass 1 1/2 years ago) and my lung doctor, looking at xrays and breathing test results, says i have minor COPD but not enough to cause this problem. should i be taking some other type of tests? should i be seeing another type of specialist? .