3 week old always hungry?

My baby is 3 weeks on Tuesday and I feel like he is always hungry and never content. I am breast feeding and don't think it's an issue with my milk as it will happen even if I give him an expressed bottle. He has had 150ml (5 ounce feeds) and I have seen him chew his hands not long after which is how I know he's hungry. Just now Iv given him 100ml expressed and he finished it and cried until I put him to the breast. He's been there a while now still feeding. Is this normal?