7 week old suddenly not hungry, concern?

Nynke • Dutch, teacher & mom of Teun 30-3-19

Hi! My little guy is having a bit of a weird day. He seems happy and content but not hungry at all! Usually he wakes up hangry and finishes 150+5 bottles. But since this morning he only drinks half or even 1/3 of this (6pm here now). Should I be worried?