Welcome to the CFS message board!
I'm sorry to hear you're having all these problems. I know you said you're set up for a 2nd opinion, and I would suggest that you let that Dr repeat all the blood tests, if you haven't repeated them already. Mistakes do happen, sometimes, and with a difficult case like yours, it's important not to miss anything.
Well, your symptoms are consistent with CFS. CFS is a diagnosis of exclusion, meaning that there are no tests to indicate CFS, and the only way to diagnose it, is to exclude everything else it possibly could be. And the ANA test is often the key. Many, many people with CFS look just like an autoimmune illness. And based on info shared in support groups for chronic pain, with people who have autoimmune illnesses and CFS/FMS, their illness experience sounds almost identical, to me.
Like you, I had every test, some 3 or 4 times. And it was not just me who couldn't believe the test results. Eventually, several different and unacquainted Drs, also thought autoimmune of some kind. But no, my ANA has never changed. Every now and then, there is some short amount of time, between when the symptoms develop and the ANA shows positive. So it's possible you'll turn up positive in the near future. But I don't know how often it happens, or how long that time might be.
The one thing you say in your message that grabs my attention is the rash on your elbows. There is a very common type of rash that occurs on elbows and some other areas, I can't remember which other areas at the moment (although I think ankles is one of them). I also can't remember the name of the rash, for sure, but it's either eczema or psoriasis. And there's a rare autoimmune disease that involves one or the other of those rashes. I'm sorry I can't remember the details, but if you visit a dermatologist, they would be able to tell you more about it. (I don't know if the ANA is used to diagnose this particular autoimmune disease).
Then there's one other thing that I'm impressed with, and that is how you have symptoms from a number of different autoimmune diseases, and it happens that there's a disease called mixed connective tissue disease (I think that's the name), which really is a combination of several autoimmune diseases. But I'm pretty sure the ANA has to be positive before one considers Mixed Connective Tissue Disease. And again, I thought I might have this as well, but my ANA was only one suspicious, but never again positive.
In the end, as frustrating as it is, not to have a diagnosis, or to have CFS as a diagnosis, these autoimmune diseases do not carry a very good prognosis. With CFS, I think we suffer almost as much as those with autoimmune diseases, but there is no evidence of shortened life span. In the end, autoimmune diseases progress ruthlessly, where CFS stays about the same, with fluctuations, but the progression is not usually life-threatening (although in rare cases it is).
Guess that's about all the insights I have. Wish I could have been more helpful. Good luck, and let us know how the 2nd opinion goes.