Welcome to NeuroTalk:

It sounds like you have significant motor problems, is that right?

Normal test panels do not automatically test for B12.

I think you need to do that first thing, and get the test numerical result. Do not accept "normal"...as ranges in US are not updated to the new information and treatment. The lowest normal now is 400. And with symptoms like yours, you should be at 1000 or more.

Here is the B12 thread, explaining methylcobalamin.
http://neurotalk.psychcentral.com/thread85103.html

What is PE? Did you mean PN? If you'd like me to change your title (you cannot edit that yourself) I will do that for you.
You can edit your posts for 24hrs.

If possible think back to a trigger for all this. Did you take antibiotics for an illness? Have a stomach virus/food infection, flu or other infection. Get a vaccine?
Injury, exposure to something noxious like solvents, pesticides, etc? Do you take statins for cholesterol?

A rapid onset PN with substantial loss of function requiring a walker in 2mons suggests a CIDP...which typically is autoimmune, and often treated with IVIG.

Perhaps you need another medical opinion?