My original pulmonologist told me "MAC is slow... to grow and slow... to go." Not what we want to hear, but I bet I had it for 3 years before diagnosis. After four months on antibiotics I started to adjust to the meds and feel a little better.
Unfortunately, I did not convert to a negative sputum culture, so after a year I was prescribed the Big 3 DAILY and felt worse. Now, 6 years later, they would be talking about Arikayce - I think people now have a lot better chance of clearing.
Are you also doing daily airway clearance? Are you using 7% saline?