My son has been on formula since 4.5 months, he is now almost 7 months. We have gone back and forth between similac pro-advance, enfamil neuro pro, and the store brand for both. We started out with similac and the store brand of it but then got a case of the enfamil for free and decided to try that, went back to similac after it was gone and realized the similac gave him really bad constipation. We went to the enfamil store brand and now he is spitting up and fussing a lot. I am hesitant to try the sensitive or gentle formulas because of the added sugars but I’m not sure what to do beyond that to keep his digestive system running ok. Any suggestions?