Eve, Wait just a damn minute!
You're making an awful lot of assumptions here. There is no way to tell what the doctor will say or do or not! Are you one of those people who need to know the end of a movie or book before you see or read it?
ME/CFS and MG are completely different animals. And a good doctor will methodically go about trying to figure out exactly what a patient has. Or not.
You obviously have fatigable muscle weakness. That is NOT the same as "feeling" fatigued after an activity, as in ME/CFS.
You're in the UK, right? The number of people in England and other Northern European countries who have CMS is relatively high. Have they considered that this is a genetic disorder? Does anyone in your family have similar symptoms?
It still could be MG. Not many doctors can conduct the SFEMG well. AND analyzing it takes hours. It's not as great of a test as doctors would have us believe.
MG is a clinical diagnosis that is backed up with tests. A negative proves NOTHING. Your dramatic response to Mestinon, however, is highly indicative of having MG or a CMS.
The reason Mestinon "wanes" is because the more you do, the weaker you get! Mestinon works great but it will not stop weakness from getting worse the more you do!!! It's similar to thinking acetaminophen will help mild back pain AND a raging headache. It would probably help the back pain but not the headache.
The severity of MG is what waxes and wanes, and that's why people who have more severe symptoms need immunosuppression instead of only a "helper" drug like Mestinon.
You need support right now. We're here to help, whether or not this ends up being MG! The MG diagnostic process can be long and frustrating. There is absolutely no need for you to go through it alone!!!
Even if the SFEMG is negative, that does not mean that you don't have MG.
I highly suggest that you spend a day pampering yourself, and not thinking for one millisecond about doctors or doctoring!

Annie
http://www.meassociation.org.uk/abou...osis-of-mecfs/