My 1 year old daughter has been fighting with constipation for a couple weeks now, ?

She's in obvious pain I usually hold her and bring her knees to her chest when she finally goes its hard as a rock and sometimes there's a little blood....I don't know what to do, I give her prune juice but then she has bad diarrhea I haven't changed her diet so I'm not sure why she's getting constipated. I'm a first time mom, any advice will help please!