@stew80 I have been going through the same thing for the past 11/2 years. I went to my primary, he sent me to my cardiologist, cardiologist sent me to Abbott for a Angiogram and ct scan.
Xray lead down the path of stage 4 lung cancer. Started treatment in October with Chemo and Immunotherapy. After 6 months still complained of continuing shortness of breath. Oncologist insisted this was not from the lung cancer or the drugs. I went back to my pulmonologist, she tested me more specifically for other causes of my shortness of breath. Turns out it is COPD and Emphysema. Something I don't want to have but I am no longer looking for the cause.
I was given two types of inhalers, they help but certainly no cure.
I hope you find your cause.