Constant Constipation

My poor baby is ALWAYS constipated. She hasn't had a normal poop since before the 4th of July. I started giving her prunce juice, 1oz and she would go and it would be hard and awful. Then she would go and it would be more normal. So I would stop the juice and 3 days later start the process all over again. And the first poop is always hard and formed together. And she screams when she goes. So I decided to give her the juice every day even if she goes because she obviously isn't going without it.

So now I've been giving her prunce juice every day and it's not even working anymore. She went a little hard amount on Friday and hasn't at all since then. 

I know they say baby enema's are bad because her body will rely on them to go but I don't know what to do. The Dr. brushed it off and said to try the dark Karo. Which I will tomorrow. But this is clearly an ongoing problem.

She's FF and has been since birth. Same formula. I don't know what's causing it or how to help her. Any thoughts?