When I had my first baby I also was on only prednisone and mestinon. I was not allowed to breastfeed as the MG went from ocular to generalized postpartum due to the hormonal fluctuations. You have breastfed for 2.5 months which is wonderful because the newborn gets the good antibodies from breastmilk in those first few weeks. It doesn't hurt to use formula in addition to breastmilk so that if something happens to you quickly a caregiver can give your baby a bottle without having troubles. I was too weak to hold my baby or the bottle and my husband had to feed him. As I got better I cuddled him a lot to satisfy his needs and my guilt over not breastfeeding. I 2would talk to my neuro and OB to help you make those decisions. Good luck.