Yes, you can consider a skin biopsy.
Everyone has "trigger points"... so I can't comment on yours.
Fentanyl is not an option, and I don't think a doctor will give it to you.
Lidoderms cannot cover your whole body, and are not indicated either. Central drugs like Neurontin/Lyrica and/or Cymbalta are offered to help you not pay attention to signals from the body. They don't change whatever is causing the misfiring however.

The Mayo Clinic information on this, pityriasis rosea states it may be due to a virus in the Herpes family. HHV6 or HHV7. I believe you can be tested for these to see if you have elevate titres. If elevated, perhaps an antiviral would work. No guarantees for that, though.

http://www.mayoclinic.com/health/pit...ents-and-drugs
All I see on this rash is that it may be "itchy"...and is common and goes away.

There is one skin condition, that is connected to PN... it is intolerance to gluten. The skin condition is called dermatitis herpetiformis.

http://www.csaceliacs.org/dh_symptoms.php
Your pictures don't look as severe as this, but you might have photographed them at a different stage.
This rash comes from the allergy to gluten, and blood tests exist for diagnosing it. They are not allergy tests, but IG tests and this one:
http://en.wikipedia.org/wiki/Anti-tr...ase_antibodies
Not everyone with gluten intolerance gets its however.
There are blood tests for this too. Gluten neuropathy does exist and some here in the past have had it.