switching milk

Hi sis ung baby ko is 6 months old nung 24 so i decided to switch the milk nya kasi sabe pwede na raw kasi 6 months na .from s26 to bonnamil tapos now sobrang hirap nya mag poop sobrang tigas ung nde nya nailaabas at naiyak na sya . Constipated po kaya sya dahil sa new formula na binigay ko or dahil nag start na sya mag solid food pero no intake of water ayaw nya po kasi lasa ng water e.