Dfrojas,

I wonder if it could be along the lines of Lambert-Eaton Myasthenic Syndrome (LEMS)...? Symptoms can vary but I know most if not all your symptoms are related (e.g. burning sensation, eyelid drooping, muscle twitching that comes and goes, regaining muscle strength upon exertion,..)

For LEMS, you could try the VGCC receptor antibodies blood test. People with LEMS might also respond to the prescription drug Mestinon or to the Tensilon test. Was it a single fiber EMG (SFEMG) that you did? That's a way to check for it as well.

Here's the Myasthenia Gravis group which includes patients with LEMS. The group is VERY active and even more helpful, you might ask them: http://neurotalk.psychcentral.com/forum77.html

I hope you can get this resolved soon.