Yes I suffer from this. I’ve had several lung function tests, x-rays, several heart monitors attached to my chest for a period of time and a heart stress test. Nothing! I’ve come to realize it’s most likely a combination of having costochondritis and severe stomach issues including gerd and trapped air that doesn’t go away. I have hiatus hernia, but doctors say it’s minor. I understand what you mean about the breathlessness being different than asthma. It’s hard to explain to others. I get it completely. I’ve been dealing with this for several years and it is tiresome to say the least. I hope you find answers real soon and get some relief .

Hiya Trevor, how ya doing.
The breathlessness is awful, it proper gets me down. Makes me feel like an old women

I dnt know if it's the fibromyalgia or my hiatus hernia going into my chest. Because I'm not out of shape

I get breathless from so much fatigue and anxiety

Thank you! I do think it my sliding hernia because my stomach is up in my chest constantly pressing on my heart and lungs, I've been waiting months new for results from an acid measuring test, to see if they will operate. Hope you are well otherwise 😊