Have You been checked for a possible cardiac issue like Congenital Long QT Syndrome
. I've been studying this for 12 years, and some people with CLQTS are misdiagnosed with exercise-induced "asthma". Please get an opinion from a cardiologist who is familiar with CLQTS and other similar heart issues.
My daughter would probably be alive today if she had been diagnosed properly.
That was 12 1/2 years ago, and much strides have recently been made in diagnosing this. It's not just what tests are ordered but who reads the tests that are important. It needs to be a cardiologist who will hand measure your QT interval, and knows how to calculate the QTc Many doctors are woefully lacking in knowledge of CLQTS and similar cardiac conditons.
Good luck and don't give up on getting the proper diagnosis.