Jen-
I am not sure what could be causing Andrew's reflux, but a lot of us here have had feeding problems with our little ones too. My daughter, Sophia, could hardly keep anything down as an infant. She ended up being diagnosed with a milk allergy at eight months that solved a lot of the problems. But most cf kids have reflux without the milk allergy. If you haven't already, make sure that Andrew sits up for about 30 minutes after a feeding. Also, Prevacid seemed to help my children. Did he start on enzymes?? Hope the GI doctor can give you some guidance.
Sharon, mom of Sophia, 4 and Jack, 2 both with cf