She's all backed up -- no poop since Wednesday

Tonight it definitely started to bother her and she freaked out before bed and wouldn't eat. I called the pedi and they said to give her diluted prune juice but by the time I got back from going across the street to buy some, DH had calmed her down and put her to sleep. I guess I'll try it in the morning if there's still nothing doing. Anyone else have this problem?
Re: my poor kiddo
We just tried the diluted prune juice and she wasn't too into it. I got a little more than an ounce into her so hopefully that'll be enough. Tried some tummy massage, too. Who would've thought I'd be so excited for her to poop?