I'm wondering what kind of doc did the tests and how many tests they were. Aside from normal "full" bloods, I'd expect just normal rheum / hormone type?
A centre for rare diseases once did a panel of bloods on me with 11 test tubes turning out 5 pages in very small print, but even in that quite a few of the ones in which I now know I am deficient were missing. They were suggesting Sjögren's and/or Hashimoto's, but both were then excluded thru further testing. So is autoimmune or immune praps something for you to still think about whether or not it's "all been checked"?
Fibro brought me flares of a strong feverish
feeling, but my temperature was axillar still about 35,5°C and above.
That made me think about something autoimmune or immune and try cold showering it away until I realized it's tiredness and learnt to sleep better.
The jabs brought on long term immune system overreactions, the MCAS
@Cutiegirl asked about this Tuesday
here.
This for me is causing long term low grade temperature of 1°C or more higher than my usual.
You're not talking about a feverish feeling nor a "low grade temperature" lower than "normal".
But MCAS does have a low grad temperature like you're saying and can't be tested easily. However a lot of other symptoms which you aren't mentioning.
I don't find it helpful to blame things on fibro, and so wouldn't want to hinder your quest at all, but if the autoimmune hypothesis were true for at least some of us, then I'd expect low grade temperature in those or at least I wouldn't be surprised.
If we search for "fibromyalgia and low grade fevers" there's quite a few anecdotal mentions. Also some studies, e.g. "Psychogenic fever: how psychological stress affects body temperature in the clinical population" by Oka, 2015, and "Fibromyalgia Flares: A Qualitative Analysis" by Vincent et al, 2016. But when you look at the studies these refer to, they are pretty worthless, again a few case studies, often naming CFS rather than FM. The 'psychogenic' one is an easy one for you to check for yourself, the easiest example: "A 26-year-old female nurse with CFS noticed that her Tc became higher (up to 38.5°C) when she felt stressed at work." - they did a stress interview too measuring various bloods and again the temperature increased. Healthline prematurely concludes "Psychogenic fevers are most common in young women and people with conditions often exacerbated by stress, such as chronic fatigue syndrome and fibromyalgia." I couldn't find one example without CFS involvement, and only a few case studies.