How Long has been already? Are you feeding every 2-3 hours now?
It could be just a phase.
You can try feeding every 1-2 hour for 60ml in the day.
Even baby drinks let say 20 ml, you may paused awhile after 15 mins - 30 mins, let lo drink again. Try and error.
Check his tummy has any colic?
How’s lo poo or pee?