Myasthenia Gravis Support Group
Myasthenia gravis (MG) is a neuromuscular disease leading to fluctuating muscle weakness and fatiguability. The hallmark of myasthenia gravis is muscle weakness that increases during periods of activity and improves after periods of rest. Although myasthenia gravis may affect any voluntary muscle, muscles that control eye and eyelid movement, facial expression, and...

I also had double vision, but never had eye pain when I turned my eyes. The muscles that control eye movement tire, and can't hold the two eyes lined up with MG and thus the double vision.
The sore eye may be related to eye muscles. If you close your eyes and rest them, with MG, sometimes that makes them OK for a little while -- our muscles work, but tire very quickly.
Some doctors will let you try Mestinon (pyridostigmine) a medicine that makes things much better for most folks with MG in about 1/2 hour and lasts for a few hours (sort of like how an aspirin works for pain). You might ask to try this as an experiment -- often just one pill will make a great deal of difference.
Good Luck Russ