H.B.
Hi T.!
If there is one thing that I have learned having a baby, they go through so many phases! Your son is probably going through a phase where he is just not that hungry for the formula. My son does the same thing, only it is with baby food and table food! There are some weeks he will eat so much and barely any formula and then there are some weeks that he will only eat formula! It can be frustrating, but don't worry! Babies are just like us, they go through phases of being really hungry and not being really hungry! Also, he is getting to the point where he won't need the formula anymore, so maybe he is making the weaning process a little easier on you! Unless he doesn't eat much real food and starts to lose weight, I wouldn't be concerned! But if it really concerns you, then call your pediatrician! Hope this helps!
H. B.