My ds was on Nutramigen AA and got very constipated and gassy. We switched to Elecare and he is doing much bettter. Our nutritionist said that while the elemental formulas are basically the same, some kids do better on one than another. She told us to try another one (Either Elecare or Neocate) and see if that helps. You might try doing the same. And at least for us in the US Elecare is so much cheaper than Nut. AA! It might be worth looking into. Good luck!