It sounds very similar to my experiences before I was diagnosed. I had a lot of respiratory troubles, vision difficulties, would be holding my phone or other object and all of a sudden it would fall from my hand...most of the symptoms were transient and mild, until my second pregnancy and then even worse after delivery when I couldn't ignore/dismiss them anymore. I have noticed that I have a lot of generalized fatigue, but in terms of my limbs my left arm gets particularly weak and tingly when the all over fatigue is at it's worst. Not a single MG related test came back positive for me, but the symptoms all of it improved with Mestinon, so my neurologist confirmed the diagnosis.