Normal idk what to do

My baby is 3 months and a half and this week from Sunday it’s not eating very well.Usually got around 780/750 ml formula in 24h and now barely gets around 650/700.

Doesn’t seems ill and wets the diaper.Screams and coo s a lot.Sleeps like 20min wakes up starting to coo and scream ( a scream not from pain but like wanting to talk ) Seems in a good mood tho so i’m not sure if not eating has anything to do with it or not.For example i try to feed and gets 80ml and then starts to smile and to coo and refuse the bottle then i try after like 30min and eats again the rest of the bottle or another half.Only formula fed and i’m a FTM. i’m not sure if i should be worried or not .