Hi Lucy -
I'm glad you are getting some helpful responses. I'm no help with psychological things, not meaning that your problem is psychological either, but IMHO it's worthwhile to continue to try to find a physical answer to your problem! Doctors don't know everything and often don't believe patients. But some of it probably our fault, sort of, for not knowing the right words to use when explaining our problems. I know I don't know enough to get some of my points across!
Do you have reactions with everything you eat or drink, or are there things you tolerate? Have you tried keeping a food journal to see if you can find out if you have specific food triggers?
My GI doc still doesn't believe, and I suspect my heart doc doesn't either, that I get gastric reflux, which triggers tachycardia, which triggered coronary artery spasm, which was the reason for my heart attack several years ago. I realized my stomach and heart problems occured when I ate some meals, drank some things, but not everything. I finally found an allergist, the second one of those, who got me keeping a record, and it was the key for me! Once I had a list, I was able to find my foods on several websites of sulfite intolerances. Not that that's your problem!
Since finding one sensitivity, I have realized I am also sensitive to lactose and wheat, although those do not cause all my reactions. They do make me feel bad and give me gas, which hurts.
Another way to play the game: Theoretically, rice, lamb and pears aren't supposed to bother most people. You might try those first, then add one food at a time.
This is just an example, so keep on plugging!