Hi, badar. Welcome. You know the penis has muscles that control it too.

I suggest you speak to your primary doctor and possibly a urologist. You want to make sure exactly what is going on first before you throw a drug at the problem.
I honestly don't think it's the Mestinon. Again, talk to your doctor and try to figure out what's going on first. MG can affect any of the 640 skeletal muscles in the body, especially those that are used more often.
Annie