Constipated

My baby is turning 1 next week n her dr said to give her milk I gave her vitamin D milk n she’s been constipated :( she cries a lot obviously lol bc it hurts I give her water n he told me that just keep on giving it to her that she will get used to it n to give her prune juice n pear juice... it sucks seeing her like that 🥺 then the only way she will sleep is if I give her milk she won’t drink a juice to sleep or water just milk :/ I give her regular food during the day too