Can't breath. it's not asthma/copd or fibrosis or cancer or anxiety. i have been tested. worst when hot, i cool off its slightly better. lactic acid?

Competent examiner: There are a great many different causes of shortness of breath, and to find out what's going on with you, a skilled physician needs to start with a good history and physical exam. It can be anything from a narrowing of the trachea to pulmonary hypertension. Please don't waste time on pop-nonsense "lactic acid" websites and so forth. Perhaps your local med school clinic is your next place to go.