Start keeping a blood sugar log (like a diary). Check it every morning, before a meal and 2 hours after you eat, and write down a short summary of what you ate all day for a week or 2. Then take that to your doctor. If your cf doctors won't listen, ask to be refered to an endocrinologist.
Here's you a link from the Cystic Fibrosis Foundation about CFRD:
<a target=_blank class=ftalternatingbarlinklarge href="http://www.cff.org/UploadedFiles/LivingWithCF/StayingHealthy/Diet/Diabetes/CFRD%20Manual.pdf">http://www.cff.org/UploadedFil...etes/CFRD%20Manual.pdf</a>