I too am seronegative. All blood tests were normal, but diagnosed with generalized MG by SFEMG. I am on 90-120 of Mestinon daily and 30 prednisone. Mestinon alone worked for awhile, but then wasn't doing as well. Prednisone has been extremely helpful, despite shakiness and munchies. Over the last two weeks the doc tried to reduce the prednisone, trying to get me to a lower level by reducing 5 mg per month. I only made it two weeks on 25 before my pre-med symptoms returned. So now I'm back on 30 and working to get a thymectomy scheduled. You're not alone and I wish you the best in finding a good balance of meds.