Re. CF & colonoscopy; if results were all normal it wouldn't seem there was anything there that would suggest CF to them. CF is generally dx'ed through other means (although there are occasional complications associated w/ CF that might be seen/addressed with this test.)
Re. celiac disease: an example of the blood test that can be done: <a target=_blank class=ftalternatingbarlinklarge href="http://www.questdiagnostics.com/hcp/topics/gastroent/celiac.html">Celiac Disease Comprehensive Panel</a>. If it was done, you would have been told, I would think. This dx is confirmed via an upper GI endoscopy, (not colonoscopy), along with a trial of a gluten-free diet.
To be honest, given your set of symptoms I am surprised your dr did the colonoscopy but did not do any other testing for some of the more common gi disorders or allergies (food and respiratory), etc. I hope you can get this figured out, whether it's CF or something else!