constipation

Hailey • Mommy to 3. 5/18/16 💗& 9/20/17💙. 8/11/20 💙
My daughter is and pretty much stays constipated. She is about a week shy of 11 mos old. This has been and issue for several months now. 
I've tried prune juice, apple juice , Karl syrup - none of which have helped
She pushed and pushed tonight and you can see the poop it is just way too big and hard to come out. It breaks my heart.
Dr prescribed milk of magnesia and it helped for a little while (he prescribed 2 weeks of it) and then I stopped doing its job.
I've used the liquid glycerin suppositories and they help on occasion. 
Any other ideas??