confused and concerned

hey there, i just recently had my third child this pass nov. she was born 5 weeks early. she was placed in the nicu for 10 days due to respiratory failure and pneumonia. since she has been home she has been completely healthy except for constant diarrhea and failure to thrive. but we changed her formula and she is doing better except that she stays extremely gassy. a week after she came home the state health dept. called me and said she tested positive for one mutation of cf. after talking to my husbands family we found out that my husbands fathers first cousin died from cf but there has been no other known family member with it. we just recently went for a sweat test this pass friday and her test were borderline. so they want us back this tuesday to meet with a team of pulmonary doctors and more blood work and stool samples. has anyone else out there had a similar experience with good results. this is just so frustrating because her symptoms could be related to prematurity and milk and soy allergies or cf. my other two children were not tested with the new born screening because they just added that one to our new born screening this pass year. my 5 year old son though has suffered with constipation since birth he was just recently referred to a pediatric gi doc. they didnt suggest testing my other two until we hear the results back from her.