Formula switch

Poor bub. We started out on Enfamil neuropro and qualified for WIC. So we are in the midst of switching to Gerber Gentle. So far it has been rough, extra gassy, more painful to poop. I just don’t know how long to give it to level out. I have been mixing them to switch instead of going cold turkey. Sadly our area will not supply anything other than Gerber, not even with recommendations or prescriptions from our pediatrician. I want to give it plenty of time but we will just buy the Enfamil if need be.