Hi, mimc. Come on over to the MG forum and we can help you out, okay?
Mestinon is not normally used for fatigue! It increases the amount of acetylcholine (ACh) getting to the muscles by blocking the enzyme acetylcholinesterase (AChE). AChE's job is to mop up ACh after it's done with its job of making muscles strong.
Was the doctor who prescribed it a neurologist? If so, OMG!
When muscles are weak, doctors say that they're "fatigued." So, in that case, fatigue does not mean sleepy tired but weak. Does your doctor think you have weak muscles? If so, then s/he should've figured out the cause of it before throwing a drug at your symptoms. And it's not the right drug either!
Provigil is often given for being tired for diseases like lupus.
Have you had your B12 or thyroid checked? Do you know the cause of your PN?
If I - or we on the MG forum - can help in any way, please holler!

Annie