Have you been to a pulmonologist? If not, please find one and go. They can asses your breathing and help you!

They should do MG-specific tests like MIP (maximum inspiratory pressure) and MEP (maximum expiratory pressure) to see how well you are doing at breathing in and out.

Why are you concerned about breathing through your nose versus mouth? Is something else going on? When my breathing gets bad, I do have more trouble breathing through my nose and will breathe through my mouth.

PLEASE, go see a pulmonologist.

Annie