Update! I got a copy of everything the rheumatologist sent to my GP, including the results of the blood tests. There are some abnormal results, but just from looking them up, they don't seem to indicate anything specific. Also, he writes that I don't have acute Lyme, and that an "inflammatory-rheumatic systemic illness / vasculitis" (not sure if that's the right translation) can be ruled out (also, no hypermobility). I'm not sure where that leaves me. I still have the appointment next week, and I hope he'll tell me something helpful then. But right now, I feel actually a bit disappointed - not that I /want/ to have a bad illness, but I'm already feeling really bad, so I'd at least like to know why (and hopefully be able to do anything against it.)
(My sister has a pretty bad coenzyme Q10 deficiency, and that can be genetic, so I'm going to ask my GP next week to be tested for that. I just wanted to wait till after the rheumy appointment in case he has any better ideas.)
According to my mum I should be glad it isnt lyme or whatever else he tested for, but I'm just feeling really down right now.