Thanks so much for the reply. I can't believe it's taken you 20 years to get a diagnosis, that must've been terrible! When you're well you just assume that if you ever fall ill you'll be given a diagnosis and treated, but this really doesn't seem to be the case for so many people. I've looked as mast cell activation before as a lot of the symptoms do fit, and tried benadryl for a while, but when I got a referral to a rhumatologist as I suggested the possibility of ehlers danlos at the time, I just had the first consultation with them but they discharged me, saying that they didn't think it was anything autoimmune???? I guess it's just finding that right doctor, who's either seen something similar before, or who actually cares enough to refer you to the right people to get the help you need.
I did keep a food diary for a long time, but didn't notice anything to do with what I ate, though it might be worth doing again at this stage.