Medication change from clarithromycin to azithromaycin

I have been on the Big 3 for 10 months, and have been having increasing gastrointestinal issues and more weight loss (after 4 stable months). As well, I continue to have cultures positive for MAC. Sensitivity testing still says the Big 3 should be working.
Color me frustrated.... Referred to the Infectious Disease doc for the first time.
He suggested a change from clarithromycin to azithromaycin to see if I tolerate it better. And indicated he sees the treatment regimen continuing for up to another year.
My questions:
Has anyone else had this change to the ...mycin, and did it help gastro symptoms and/or weight loss?
What other avenues are available to step up the effectiveness of the protocol?
We are repeating the CT to see if the lungs have improved. I feel like I'm just "maintaining" as far as cough, sputum, energy... My weight is nearing 100lb, and I cannot afford to lose any more as I already feel like I'm nearly a skeleton - ribs and pelvic bones visible, facial bones prominent & skin loose...