baby feed

Trish
My baby is 4 months and recently developed habit of drinking milk when sleeping. If he's awake 8 hours he would not touch milk(bottle fed breastmilk) never finishes his bottle, I dono how many times he feeds as he will take 2-3oz at anytime and I have to be after him when he's asleep so that I feed him before he wakes up. Is this abnormal ? What can I do to change his habit ? It gets so difficult to make him sleep only cuz he is not fed and he won't if awake even though is he very hungry 🙁☹️ any suggestion is very helpful