Trying to figure out how accurate the sweat test is before tomorrow

My son is 6 months old. Since he was born something has always felt a bit "off" for lack of a better word. His stools have always been bright green with mucus, he's had a chronic cough that is consistantly getting worse, he was always crying until about a month ago, he's always breathed funny, and he is always congested. I've been to several doctors, most of whom blew me off and told me it was a milk allergy or reflux. I tried reflux meds and a total elimination diet at first for months but neither helped. Finally I found a pediatritian who listens to my concerns. She sent me to a GI specialist who didn't feel like this was CF and kind of shot me down when I mentioned it because he's small but he was steadily gaining weight at the time. He did some blood tests and a couple of stool samples for parasites and sediment rate and concluded that he couldn't find anything wrong with him and that he was just a "fussy baby" who would grow out of it. My ped decided to send me for a sweat test anyway which we are getting tomorrow at a CF center in Chicago. My question is, he doesn't taste salty to me so does that mean the sweat test will be normal? My insurance refused to do the genetic blood panel unless his sweat test came back positive and we can't afford to pay for it out of pocket. The lab tech said it would be around 3k. I'm just concerned that the sweat test won't be accurate because he doesn't seem overly salty.
Source: Cystic Fibrosis Newly Diagnosed Forum - Category: Respiratory Medicine Authors: Tags: Newly Diagnosed Source Type: forums