Some of the testing is to rule in /out other possible causes, to narrow down the list more or less.
Have you had a basic workup for any possible spinal issues, so that can be ruled out as a cause?
Pinched or entrapped nerves are a treatable thing, so finding those things that can be treated is a plus, vs PN dx of unknown cause.

Perhaps the dx process is complicated by the long term chronic fatigue, do you have any fibromyalgia sx too?

You may have to tell the drs how it is impacting you.
You may have an option of short term disability thru your work place. Pretty sure a dr has to rx that time off.

We have a SSDI forum with info on how to start tha6t process and what is required. see the sticky threads above the main post listings there -
http://neurotalk.psychcentral.com/forum28.html