Lois, regarding:
"I'm not sure if the MG has actually gotten a little worse, or if my body has gotten adjusted to the Mestinon so that I need to keep increasing the dosage to get the same effect."
Number one, I really understand what you are saying here. I am the same way. However, I don't think I can increase my Mestinon anymore. I take 1 1/2 Mestinon tablets every 3 hours (90 mgs). If I take anymore or closer in time I get those ill effects. About my 4th year into having MG my Neurologist suggested I try taking 1 1/2 tablet every 3 hours instead of 1 every 3 hours. At first I noticed an improvement with occasional ill effects and now I think I am used to it. Originally, I started out taking 1 pill every 6 hrs or so and gradually increased the amount and decreased the time between dosages. I don't have ill effects very often anymore, but if I do, I take 1 to 2 Imodium (usually 2 does the trick) and then I am somewhat constipated for a day

Oh well

Also, I need to have food in my stomach and will eat crackers, or if too weak I will drink milk or Ensure (usually drink one Ensure a day) with my Mestinon.
I only take Mestinon. I usually take 1 1/2 pills every 3 to 4 hours depending on how I feel. I do know that REST is like medicine for me. Sometimes, if I feel
extra out of breath and/or
real weak and fatigued, and it is time to take another dosage, I lay down FIRST of all. Then, sometimes I take my Mestinon or wait 30 to 60 minutes (when I usually start to begin feeling better). It is sometimes too hard to swallow my pill, also. That is why I wait the 30-60 minutes.
Also, I like to exercise about 30 minutes at least every other day and that seems to help me feel better.
Hope this helps.