8 mo old stool question?

Charity • Wife. Mom of both💙💗. Currently pregnant with twins🤰🏼.

My 8 month old has extremely hard stool, he won't drink juice and has been refusing all baby food lately so feeding him prunes etc is also out... is there any thing else I can do to help loosen his stool? He will go a couple days with out pooping then when he does its not much and extremely hard...(TMI: like i can squeeze the poop inside the diaper and it's like really hard clay). Needing some advice asap! Thanks!