Your baby seems to be having colic. He is only 9 days old and it is rather early for him to be having the usual infant colic that is so common in babies up to about 3 months. It is difficult to answer your question as to why he only has these cramps at night.This is also unlikely to be due to reflux.
Try your baby on an anti-colic formula such a Novalac AC and see if this helps him.
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