I have the same experience, though not as extreme as you describe. I think of it this way: MG makes your muscles fatigue faster than normal. If a healthy person lifts a weight and holds it up, after a while, his arm muscles will tire, and he won't be able to hold the weight up any more. That's muscle fatigue. With MG, this fatigue happens much sooner. Using muscles when they're fatigued makes them stiff and sore, no matter what the reason for the fatigue is.

If a healthy non-athlete spends the day mountain-climbing, he's going to be stiff and sore the next day, because he worked his muscles past their normal capacity. For a person with MG, day-to-day activities work the muscles past their capacity. So we get stiff and sore. On Saturday I cleaned my kitchen cabinets, which involved climbing onto a chair and back down a bunch. Sunday, I felt like I'd been, well, climbing a mountain.

You should definitely discuss it with the neuro, because I'm only guessing--there could be another reason for your symptoms. But sure, MG "only" causes weakness. But over-exertion of muscles causes pain and stiffness--and weak muscles get over-exerted much sooner than strong ones do. Doesn't that make sense? A neuro who doesn't get this needs to get his nose out of his books and think like a normal human being. It's just common sense.

Abby