Hindi Makadumi Si Baby. Pls Help Po

Hi mga mommies ako po ulit HUHU last week kasi we started feeding our baby ng formula milk, S26 gold. Mixed feeding pa rin siya with breastmilk. Pero now he's not pooping since Monday, July 13. Sinabi ko na po sa pedia niya but all she said is observe lang daw si baby and make him drink droplets of water. Hindi parin kami mapakali though. May ways ba how to make him poop na? Thank you so much 😔 Edit: baby is currently 5 months and 14 days old