My 7 month old baby boy has been on novalac ar digest since he was 2 months old. due to this formula being so expensive, what can i use that wont constipate him? not novalac it as he vomits, s26, similac, lactogen, isomil all dont work!

Hard to speculate: The Novalac AR digest is thickened & has partially digested proteins that are meant to avoid milk allergy/intolerance. That is why it is so expensive. If he is not milk allergic, other formulas may be reasonable, but how he reacts to each will be unknown. You may just want to reduce formula to the 16 oz minimum needed for calcium intake & push his other feeds to make up the difference.