I'm sorry you are going through this. It sounds really tough.

Yes, having both diseases simultaneously can happen. It makes for a more challenging treatment strategy, but sometimes the same drugs can be used to treat both conditions.

"Lockjaw" doesn't sound very much like MG to me, unless I am not understanding what you mean. With MG, usually the opposite is the problem--the jaw is weak and can hang open. Locking of the jaw can be something as simple as TMJD, which I have as well. That. of course is more of a structural/joint problem, not a weak muscle issue.

In any case, I hope you find some answers soon, so you can begin to pursue treatment. Please feel free to share some of those other symptoms that aren't explained by MS as well.