Dear 2sickkids -
I sincerely hope that your testing is negative, but if CF is the result it may finally give you some answers to many of your ailments. Perhaps the doctor wants both results because of the many symptoms you have, and he/she wants to be absolutely certain that CF is not the culprit. It is rare, but some people do test negative to a sweat test, and later genetic testing confirms CF.
You have the choice to stay with your pulmonologist, but like the previous poster said, the CF center may provide more support and people who specialize in all areas of CF care. You can always go for a consultation visit and see what you think.
Good luck, you are a courageous mom and I know we all wish you the best.
Maria (mother of three daughters, the youngest Samantha w/cf)