I wonder if there are more tests your doctor could do to check for an autoimmune disorder. It sounds like you could also be checked for a hiatal hernia; depending on where it is if you do have one, that could interfere with your diaphragm.

I hear you about it taking a toll on your mental health. Early on when it first started for me, it certainly took a toll on mine as well. Lots of uncertainty and wondering it it would get better. As I did breathing exercises and it improved, it was no longer an issue but when it returned about 4 years ago and has remained, I learned that it's a condition that I may be dealing with for a long time. Since I now have a routine of breathing exercises and physical exercise which helps keep it at bay, my mental health has been steady and improved. I have adopted a 'it is what it is' and acceptance mindset but never losing hope that my breathing will be normal again.

I can't exercise rigorously like I used to, and every now and then like you, I would have to delay some tasks as I experience 'flare ups' of the air hunger. But I have learned to wait it out and tell myself that I will be fine and it will be better again. Knowing that there are ups and downs and knowing that the downs are temporary keeps me sane and my mentality consistent.

When it first started, I did encounter people who thought it was just in my mind or thought it was something else. I don't as much now since those around me know it's something I've been dealing with a for a while, but how I overcame it was simply to relate to people who believed me as well as others who have been dealing with certain conditions, and talk to them about it and not really bring it up to those who didn't believe me.