I've a brass neck posting an opinion when I have been wrong about my own illness so many times, but this time I think I'm right, like all the other times.
I think it's mold. Or else some other chronic infection. I think if an immune system can get into this state without a foreign biological presence, it would be able to get out. I'm reading Neil Nathan's "toxic" at the minute. He says he sees 80% of patients with complex diseases like our's as having mold issues. 20% chronic Lyme disease. And that's with a range of these "syndromes". Fibro, CFS, MCS, etc. The variation in CFS, I believe, doesn't necessarily mean a range of different etiologies.
And mold isn't something I gave any credit to when I first started hearing about it. I actually had the reverse of the thought processes I should have had. I thought "Naa, I used to live in houses that had mold and I was fine then". Yea well it grows inside you, pal.