You do not mention if your baby is being breast fed or is on a formula. Your baby is too young at 3 weeks to have actual 'colic' which usually starts at about 3 months. If your baby is being formula fed and indeed even if he is being breast fed, your baby could have a problem with lactose intolerance. If he is on a formula change him to a low lactose formula comfort formula such as Similac Total Comfort.
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