Hi, if i have shortness of breath and a history of lung problems, and keep collapsing when I exercise. I used to be able to run until a few months ago, when this got really bad after a cold/cough/flu thing. If they find nothing wrong with my chest x-rays, should I just assume I m out of shape and push myself harder? (I collapse with light exercise and I m not overweight except a few pounds of excess water retention. I also have lowish blood pressure that sometimes gets very low, and an arrhythmia when my. heart beats faster than about 95 per minute.)