Constipated breastfed baby

My baby girl is 8.5 months old and she has been on and off constipated for like the last 6 weeks. The first time it happened I called the pediatrician and they said to insert a suppository so I did and it worked instantly. But it seems like it keeps happening and I have to do a suppository to get it out. When I do she cries and it comes out long and kind of hard. Idk if she isn't getting enough to drink or if I should just lay off the solids for awhile. She hates purees and will only eat finger foods. Any suggestions??? Please and thank you!!