9 week old formula fed baby not feeding as much

[shannonmc1x]

Hi, my LO is 9 weeks over the last week he has stopped feeding as much. He is exclusively formula fed.. he was taking 5oz every 4hrs and now will feed when the bottle is given but if it is taken out of his mouth for any reason he will not start drinking again & screams until the bottle is away from him. Worried he will not be feeding enough!!

Is he having enough formula a day for his weight?

I believe he should be drinking 27oz a day and averages 26oz however in the last week since he has been refusing milk, this has surely decreased.. unsure why he would refuse bottle or become fussy when he always drank well from birth