Lindsey,
i was just like you until I was about 19 and caught a microbacteria. I ran both track and cross country in middle and high school. I only took enzymes, ADEK and a mild daily antibiotic. That was all my doctor suggested. I was also Diagnosed late. I was 12. When I went to college I stopped running. Very bad idea since I never had done any other type of CPT. I didn't know I needed to. I went to high school with two other people with CF. They were always jealous that I was so healthy. I felt like an outsider with them for a long time. I felt like my running kept me healthy. If I could turn back the clocks, I would of never stopped running. The last 10 years have been difficult for me emotional because I have had to start dealing with my CF. It was bound to happen but I was not prepared for the changes in my healthy.
When I ran I did not cough up a lot because my lungs were always clear. This is not the case any more. If I go for a walk or start to jog I cough my head off and bring up a ton.
I hope your cf stays in this mid stage for a long time. Keep running.