Feeding amount

How much do your LO’s take and how often (breast milk or formula), also how much do they weigh? Mine is 7 1/2 weeks and takes 3.5 oz every 3 hrs except at night will do first stretch of 5 hrs. He was 9lb 4 oz at birth and is gaining weight but slow, it’s how my first was too. Always just concerned with not enough weight gain (pediatrician not concerned)