TMI warning! 6 months baby constipated

ahya
my baby is on solids now and gets formula 3 times a week when i am at work and breastfed the rest of the time. she's been having issues pooping. she strains a lot and cries. she has dry poops. not rock hard but not mushy either. doctor suggested more water and prune juice/prune puree. we do that but it doesnt work all the time. what can i do to help? 
one of the photos was when she didnt poop for 4 days. when i saw her straining, i helped her by bicycling her legs and she pooped that much.