@laurasue, sorry that you have been dealing with this. So many of us know just how you feel! It's not a fun thing to have. Do you have any gastro issues that you know of? GERD, heartburn, esophagus issues, hiatal hernia, etc? Any thyroid issues that you know of? Asthma, lung function tests- I'm sure you've been tested for those? Anxiety is pretty much the 'catch-all', 'make-you-go-away' answer from doctors when they have no answers. We've all gotten that response a few times, so we've convened here for answers!

Mine, if I remember, started fairly gradually but I just noticed one day that I couldn't catch a deep breath and it never went away. It just kept getting worse. I took vitamin B-12 and iron and it seemed to temporarily make it go away, but I have no explanation for that.

Something that has helped me greatly is the Buteyko breathing method; https://www.learnbuteykoonline.net. It likely won't cure the issue but it does help a lot of people, including me. It made my SOB go away from a good couple of years, but then it came back, but I applied the method again and it helps. At this point it makes it manageable while I still search for answers.