I can only try to give you advice based on my own experience, both as a patient and as a physician.

I think you are at a point in which you have to make a serious decision:

either you trust you physicians and are just frustrated with the time it takes them to understand what is going on, or you feel that you can no longer trust them.

Only you can give yourself the answer to this question.

If the former is right, than I think you should keep them updated on your condition. If you feel that it is worse, then call them, go to the ER or what ever it takes to make them understand that you are not doing well and not just "stressed". Medicine is not an exact science and physicians can make mistakes, mostly in rare and unusual presentations. An open avenue of communication allows their timely correction. I can give you quite a few examples from my own practice for that.

If the latter is right, and you feel that what is going on is beyond the level of expertise or your physicians then you should seek another opinion. There is nothing wrong with doing that. Sometimes another pair of eyes can see what someone else has missed (this is true for everyone, and also for physicians who are just people). Also, you may reach someone who happened to have a patient similar to you. (again, I can give you examples from my own practice, in which I made a diagnosis that was missed by others just because I happened to be aware of that problem).

I think that you need more than our advice on the internet.

What is going on is clearly not simple and straight forward. Many times there are complicated acid-base disturbances that may not be readily evident. There are various metabolic diseases that can give clinical symptoms similar to myasthenia, and are accompanied by other findings, such as brain lesions and acid-base disturbances.
Like Annie said, there are many possible things that could be going on. I can "throw in the air" some possible options that could explain all your symptoms and your myasthenic clinical picture, but I may be totally wrong, without knowing all the details.

All I can say, is that I was never ready to accept unreasonable explanations from my treating physicians. It is not easy to reach this conclusion and every time I initially tried to convince myself that I may have misunderstood or got it wrong. Yet, as a physician, my approach was that it is the patient that knows best, so I took the same approach with myself. As hard as it was, taking this approach was eventually rewarding-

After a year in which I was nearly bed-ridden and required frequent respiratory support, I was gradually able to resume at least some of my previous productive life.