5 week old not eating much

Okay, my son was 8 lbs 4.2 oz at birth. Not a little guy. lol. He didn't really want a bottle while in the hospital. or the first like week even he'd barely eat an ounce. Kept projectile vomiting so we switched to sensitive formula. He did better until about 3 week the projectile vomiting started again. Negative for pyloric stenosis. At his 1 month appointment he weighed 8 lbs 14 oz. So I feel like he's growing good? Now I keep getting comments on how small he is and comparing him to other kids around his age he does look smaller. He eats 2oz every 2/3 hours and is content with that. I occasionally try 4oz, but he vomits it all up. He often sleeps through the night and even when he doesn't or i try to wake him he doesn't really eat during the night. So total a day he is only eating 12-16 oz. Is this normal?