Welcome to Mayo Connect, and our very helpful and compassionate MAC Support Group.

This infection, and the antibiotics, can indeed knock you down. Just remember what my first pulmonologist told me "MAC is slow to grow and slow to go" - hence the long term use of multiple antibiotics.

The good news is, if you tolerate the Arikayce, it is showing a track record of quickly knocking down the bacteria, then you can continue just the "Big 3" for the recommended time. Nuzyra is often added if there are other bacteria in addition to MAC in your lungs - I am not sure of the duration of that treatment.

You may find some of the links here helpful:
https://connect.mayoclinic.org/discussion/resources-for-the-abcs-on-bronchiectasis-and-mac-ntm/
As for your poor appetite - please don't ignore it. Start now to find a high-caloric-density regimen that works for you. And a good pro-biotic to help your gut biome. This is an older discussion, but very relevant. 8-10 mini-meals a day was what I could tolerate on the Big 3.
https://connect.mayoclinic.org/discussion/weight-gain-1
Low energy, malaise and fatigue are all your body telling you to rest. Try using your limited in 10-15 minute "bites" each hour - load the dishwasher, put in one load of clothes, walk to the mailbox...Try to get outside everyday for a while. It will do wonders for you spirits.

And please come back and talk to those of us who have been through it - there is a light at the end of the tunnel. We're here to help!
Sue