Breathing problems

I'm a 47 year old male and I was diagnosed with the dok7 variant of congenital myasthenia about a year ago. I've been symptomatic for a few years, but all the tests for MG have been negative. Genetic testing finally found the dok7 mutation.

I'm curious how others have experienced breathing issues. Mine started a couple years ago as a minor shortness of breath while at rest. It's gotten progressively worse. Now I'm pretty much always short of breath and I always feel a pressure on my chest. At times the pressure is worse than others, usually in the evenings. Sometimes it's almost unbearable. I have a history of heart problems, but after a recent heart cath, my cardiologist doesn't think my heart is the problem. My neurologist refered me to a pulmonologist and after an overnight oximetry test they were able to get me approved for a non invasive ventilator, which helps a lot. Also, my pulmonologist says my pulmonary function test came back nearly normal. Has anyone experienced similar symptoms with MG?