Crap, I promised myself I'm going to take a break from commenting to get some substantial work to be done, but this one is an important one.

Listen, @OP, never ever give up. I took me 7 years and a large pile of money to figure out I have Fibromyalgia (which occurs not to be what people think it is). My health was gradually worsening since I was 23 (now I'm 34 and in a middle of a multi-year treatment, enjoying first fruits of thereof). Modern medicine sucks if you have something non trivial to fight with. Doctors have no time to invest in complicated diagnosis and custom approach, pharma companies don't care about customers if these aren't coming in large quantities, and an overall level of awareness in the society about how human body should work is close to non-existent. You're on your own. The good news is that patience will probably get you there. But you need to become a CEO of your own healing process. There's no other way around it. No one is going to take that burden from you.

I consider my case a pretty complicated one, this is why it took 7 years to figure out. Meanwhile I became proficient in: neurology, cellular metabolism, brain biology, and a couple more. That's not rocket science. Having time at your hands you can learn whatever you want. If I was able in my condition, so will you. You're going to see yourself how bad doctors are with connecting the dots, and you'll (you have no choice) develop better models. That's going to also help you in your future life. An ability of thinking clearly might be the most valuable resource in the universe.

Don't be pessimistic. The chances that you have something that's incurable are incredibly low. Officially Fibromyalgia is incurable. Guess what - it isn't. Using a well proven method of eliminating invalid hypothesis, you're going to be left with a handful you'd like to inspect more. This is how one by one you're going to get to a valid diagnosis. From that point you can focus on healing and rebuilding your life.

Definitely include Fibromyalgia (seems to be in line with the symptoms you've described), CFS, Myalgic Encephalomyelitis, etc in your research. Even if you don't have any of those, people involved in that kind of communities are going to help you to track down rare diseases you should inspect in detail. This book has been fundamental in making a breakthrough in my case: "What Your Doctor May Not Tell You About Fibromyalgia: The Revolutionary Treatment That Can Reverse the Disease", Dr. R. Paul St. Amand.

The only thing it takes for you to dig out of that hole is just one person figuring it out and publishig results of his work. Even if he's alone and the health problem an obscure one, you're going to find it, so you can reason about it and test it. Again, the chance that you have something really incurable is very, very low. You'd be probably dead by now if that would be the case.

PS: Beware of diagnosis made by clueless medical practitioners. I've been diagnosed 14 times with false positive things ranging from Parkinson to ME before stumbling upon on the proper one. That's ridiculous. Doctors usually can't even understand what does it mean if something is a proof of X in their own field, so they constantly misinterpret data from scientific papers :( Not even to mention that they have A LOT of trouble with not making statistical errors.

I wish you luck, buddy. Now it's time to get to work. For both of us ;) Take care.

I don't need to conclude, I guess, than instead of looking for a way around in your work environment, all the resources should be put into finding a proper diagnosis.
PS2: There's no such thing as pain without a reason. Look for a reason, not a BS explanation about how you should proceed from now on. Solutions, not a blind acceptance of what seems to be inevitable.