Constipation

Hi mommies! First time mom here. Napapansin ko lang na yung baby ko is umiiri but no poop. Well it's been a day and a half nung last poop nya. Reading the articles, hindi pa naman regular yung bowel movements ng baby but, napapansin ko lang is that he cries after niyang umiri. What can I do to help him poop? Or ease stomach ache?