Like you said, the not knowing, the uncertainty = anxiety! I want to share a recent emotional breakthrough. It may support you in getting on with living! Which has not been the case for me as well! During a second opinion pulmonologist appointment with a leader in the field (Mac/Bx) I was hearing the oft repeated suggestion that I NOT go on the Big 3 Treatment which at this point is worse than the disease. (I'm very lucky to have caught this disease early) Wait and monitor. When I told him my family who are MDs are going to be dismayed that we aren't going straight for treating this infection, he said, "tell them you are treating. Airway clearance is the frontline treatment." 2/3 will have progressive MAC disease, worsening of bronchiectasis due to the infection. 1/3 will remain stable with a sliver of that spontaneously converting to negative MAC infection. We will monitor intensively. When worsening occurs it is immensely slow and if there is a whisper of worsening we start antibiotic treatment.
I hope you might be in a similar place and can take heart with this pulmonologist's confident suggestion which landed so well with me. I think there is a hesitancy or lack of skill by some doctors to communicate confidently and clearly about ways forward.