Hello and welcome! And, so sorry you are having to deal with all of this - I am 33 years old mother of 2, and have been sick for 3 years... So, I know how hard it can be trying to work and take care of the family/kids etc!!!

Anyhow, I agree with the others - did they check for LEMS, did they check your CPK (total ck), aldolase (those all check for myositis/myopathies).. have they done a regular EMG, MRI of your head (obviously sounds like they have done MRI's of your neck already).. Many Myasthenia patients don't test positive for the basic tests.. They can also do a repetitive stim test as well as the SFEMG...

Good luck, and keep us updated!