I'll just add that MG is a fluctuating problem and is affected by lots of factors (like stress, infection, tiredness, heat, etc). It might have stopped working for a reason other than 'mestinon immunity'. I've had times when it didn't seem as effective. On one occasion, it turned out I had an infection and the mestinon 'stopped working' until I was able to get that under control.

Don't give up on it yet. Talk to your docs as that dose is very low and perhaps just a little more drug will get you back in shape. Good luck . Your new reality may just be temporary.