I am also seronegative. I take pyridostigmine (mestinon). I take 60 mg 5 times a day. I started with just an eye droop. Mine has progressed to generalized myasthenia gravis now. The drug does not totally reverse my eye droop, but it does make it less severe. I think that a lot of us are in the same boat.

If you don't have and abnormal MRI, you don't have muscle atrophy, you have normal reflexes, myasthenia gravis is probably really high on the rule out list for a fatigable muscle weakness . I'm glad that you have an old school doctor that actually seems to know something about looking at patients and not just blood tests.