I Have Cystic Fibrosis and I Feel Like I’m Losing Too Much Weight?

I have Cystic Fibrosis and I’ve been taking all of the enzymes and medications the doctors have given me and eating enough like the doctor said (as much as I can at a time) but I feel like I’m losing weight and I feel too thin compared to other girls my age and i feel tired a lot at school. I’m still in my teens. Does anyone have any suggestions for me?