It sounds like you must have a sputum or two positive for MAC. Correct?
It's never a bad idea to get a second opinion from docs who treat the disease every day. I went to Mayo to get a diagnosis and plan and am very glad I did.
One tip-they book out a while, but told me they often have cancellations on Mon and Tues mornings and to call. I lucked into one for the next week. Good luck!