Hi, and welcome! This is a good place to be, because the disease is so misunderstood. Sometimes I tell people who ask, "I have a neuromuscular disease that's sort of like MS." I know MG is very different from MS, but MS is the closest disease I can think of that everyone's heard of. I sort of want people to know that this isn't in the category of "a little under the weather"; it's a serious disease.
I understand about losing your balance and falling without realizing what's happening. For me, that happens because my side muscles are weak, and don't automatically "grab" like they should. So sometimes when I start moving to the side, I just keep going, and then I lose my balance.
Your dose of pyridostigmine (generic Mestinon) is unusually small. Pyridostigmine has a four-hour half life, which is very short. If you're only taking it twice a day, you must be running out in between doses. Also, most of us take at least 60mg. at a time.
So, maybe your doctor has a reason for giving you such a small dose, or maybe you tried a larger dose and it didn't work for you? If not, you might think about asking your doctor if you can at least take it more frequently. it might help your voice and the exhaustion.
Again, welcome, and feel free to post here. This is one place where people understand!