Baby eats 28-30 is a day but slow weight gain

BJ

My son eats anywhere from 28-30 oz a day but his weight gain is still super slow. Pediatrician is monitoring. He’s meeting all his milestones but only gaining like 3oz a week and about a pound a month ? I don’t know what else I can do he eats almost 5oz every 2-3 hours and still eats 2x overnight.