Hi B., my name is L.. I am the mom to 5 yr old and 2 yr old boys. Boy, does your situation sound all to formiliar. We went through something pretty similar with my oldest when he was your sons age. My peds recomended Nestle Good Start because it was most like breast milk (with consistancy, grit, etc. in regaurds to the reflux; which worked great and we stuck to). But the switch between breast milk, enfamil lipil, to good start was enough to send his sensitive digestive track into cronic constipation that we battled with for almost 4 yrs. We started helping him out with a little prune juice every day (he was only 3 mo at that time). Our frustrating battle took us to a gastroenterologist. He ended up on Miralax (great stuff, not habit forming, no cramping, and not a stimulant) for a while. Anyway, long story short.....the doc said the key is to make it easy on them to "go", because if it is hard for them, straining, stomache pain, etc. then they "won't go" making it all the more difficult(those little smarties will associate pain with pooping and wont do it even as young as babies). At first I didnt like the idea of constantly having to give him something just to "go" (wheather it was prunes, fiber, or the Miralax). I thought that if that was the case then there was something "wrong" so we should just fix it. But that was not the way it worked for us. He just has an extremely sentsitive digestive track (that is getting better as he gets older :)) and needed some assistance going through the first few years. They were the hardest on him (and other little ones), going from milk to soft foods to solids to cows milk, its just a lot on their little systems. I dont know if any of this was any help to you at all, but I wish you well for you and your son.