This is all fascinating. I have had a hard time googling this because it isn't just shortness of breath for me, but almost a sense that I cannot make my lungs fill all the way, then there is a "click" as @felicityr said and I get a full stretch of my lungs. I imagine it like blowing up a balloon, but pinching it in the middle, and finally releasing the air to go all the way in.

I also have GERD or some variation. Intense upper GI issues and have a scan scheduled tomorrow.

A number of us mentioned omeprazole. I wonder if it is an undocumented side effect. I am on it as well.

I will follow this thread. I haven't been experiencing this long, but it is also not the first time.

Another thought... I am emotionally well, but I do recognize my body is under stress with these stomach issues. Reduction of stress could be physical as much as emotional. While I don't need to chill out and take a vacation, I may be under tremendous physical stress as my body is rarely relaxed with the stomach pains.

Thanks for being so articulate @gabrielm. I feel less crazy. And thanks for the encouragement to explore the Buteyko breathing. It is helping a bit. I googled "Buteyko Breathing Exercises in 3 minutes by Patrick McKeown" and watched the youtube video to learn about it. (As a new member, I cannot post links yet)