If he still seems hungry up the breastmilk or formula so he is getting nutrients he needs and not a filler.

Nothing but formula or breastmilk until 6 months and it's best not to put cereal in a bottle because it's a choking hazard.

I started at 3 months he wasn't getting full off 4 oz so once I added cereal it started satisfying him

I did at 3 months bc he had really bad colic and instead of spitting up he would like projectile vomit so the cereal really helped

I started at 3 months cause he wasn't getting satisfied and was eating every hr and a half to 2 hours

6 months unless otherwise directed by your pedi.