@becky33 - 7 months is not a very long time on the 3 drugs -- some determinants for how long it may take to improve are:
1) the extent of your NTM/MAI in your lungs. How disbursed is the disease - one lung or both? What are the extent of your symptoms and how debilitating is the disease?
2) are you taking the 3 drugs every day, or 3 days a week?
3) are the drugs prescribed in the correct dosage -- based on height and weight. A 110 lb person would probably have a different dosage than a 150 lb person.
3) besides the drugs, what else are you doing to help your lung condition -- lifestyle changes such as exercise to improve lung function, rest, etc.
As @windwalker mentioned, most treatments take a minimum of 12-18 months to show improvement. The expectations of improvement after 6 months is very bold, I think.

That said, my situation is different from most here. I was on the 3 drugs for 9 years. Thankfully, the drugs eliminated my symptoms (I was quite ill and had a very demanding work schedule for years), stabilized my health, but caused other side-effects which came and went. After 4 years, I tried to go off and within 3-4 months got quite ill again. I then took the drugs for 3 days/week instead of each day.

I have found, along with the 3 meds and vision screening, it is important to consider these:
1) check your Vitamin D level - mine was at about 4-5 and very deficient; Vitamin D is somehow associated with lung function and NTM. I take prescription Vitamin D.
2) get plenty of rest ... even if you can't sleep, at least rest.
3) EXERCISE ... anything you can do to increase your lung function. My pulmonologist hit me with this 'exercise thingy' upon diagnosis. Pilates, Yoga, Walking every other day, aerobics (if you can do it), etc etc. These DO help quite a bit!

NTM/MAC/MAI is a tricky disease . . . it moves around in our lungs, can decrease in one area and pop up someplace else. Best wishes to you.