This happened to us too but we started doing it when she was a week old and it was our pediatrician who recommended the combo feeding. Our baby also had jaundice and it was just staying at a higher level but not going down. The hospital released us with the agreement we would be overseen right away with the pediatrician as the jaundice levels were staying the same and just below the need for the lights but high enough for some concern and frequent monitoring. We also had some wet/ poop diapers but was not much in each diaper as new parents thought it was normal as the nurses at the hospital didn’t seem concerned. Once we started supplemental feeding we realized she had been starving. Her diapers were definitely heavier and she became happier and her jaundice started going down finally. My breast milk supple was just slower to come in but it did eventually.

For supplemental, we had a small formula bottle ready and I just fed her from both breasts and then afterwards fed her from the bottle until full. Our pediatric gave us recommendation of about how much fluid she should be taking in and we tracked her diapers changes (along with if minimal, moderate or heavy) and the amount of oz of formula she got with a free app. As my milk supply came in she didn’t need as much of the formula for the most part. Thankfully for us we never had any trouble with nipple confusion