I decided to post this in case you are still struggling with the same problem I had.
My breathing problem fell into two categories. Rapid onset: it started about ten minutes after eating and last 45 mins. or Low grade: This type seemed to just linger in the background and I didn't realize it was happening until I tried to climb a set of stairs or something.
After a decade of this bs - I got in to see a university doctor (which I recommend). She was a GI doc and she stained a biopsy of my GI tract to find I have "mast cell activation disorder" (close to mastocytosis). I'm now taking tons of allergy meds and Gastrocrom and I feel much better. But even my smart university doc didn't know how exactly to treat me and had me under medicated until I found a group of other pts who helped me.
If you want to check this out - do not get a blood test for it as your "tryptase blood serum" isn't accurate because it goes up and down. It's complicated. But I wanted to report back to let you know what it was for me. Good luck. If you really want to communicate with me , you can try muse meg at m s n. Put "i can't breathe" in the subject line.