Constipated screaming baby

[Butterfly Dawn]

This is the 2nd day for her like this in the evening.
We have just changed formula from Nurture to Karicare we did it slowly over about 10 days she has been on karicare for about 4 days and this is the result.
She has a small amout of food- last few days it has been very liquid farex, before that was puree apple. I am cooking up some pear for her right now in the hope that it will get things moving for her.
Yesterday I tried to give her some watered down prune juice but she spat it out- cant blame her its pretty gross. She is offered water during the day but hardly drinks any.
She has managed alittle poop, its a good color but very sticky and thick.
Help us please- she is 5 mths and we havent had this problem before with her.