Baby is constipated

My almost 1 year old has been constipated for about 3 weeks. She has hard pebbles when she poops and that’s every few days. She’s starting to get miserable and I’m not sure what to do. I can’t get her in to see her pediatrician for about 3 more weeks because he is completely booked. I have tried feeding her puréed prunes, prune juice, pears, water, apples and apple juice. Nothing has worked. I don’t know what to do to help her.