why is he so hungry?

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My son is now 3 weeks old and he eats 4 oz bottles every 3 hours but sometimes he wants more after only an hour and he never wants to stop eating. He's even downed a full 7 oz 30 minutes after eating a 4 oz bottle. And he's super fussy all the time now and he's only calm while he's sleeping. Is it normal for him to be eating so much already?