Constipation

My baby has beeb having problems with constipation for the past month. He normally does every 2 days but recently he would go till day 4 and he poops hard rock looking poop.

I've talked to the pediatrician about it during his 4 month check up, I told them that when they recommended giving water, it didn't work either. They just keep insisting it's normal because his belly doesn't seem hard.

I pulled down his diaper and showed them that there is poop trying to come out and he is trying to push it but can't seem to do it easily. Then they said he will be okay and that I can try watered down apple juice from now on but treat it as his constipation medicine.

Well fast forward 2 weeks, HE WILL NOT GO UNLESS I GIVE HIM THE JUICE. I want him to be able to go even without the juice. So I called them and they want prune juice now 2oz with water twice a day.

When I gave the apple juice this morning, he literally pooped 3 times already. First one was hard, second was soft, third was close to diarrhea looking poop.

As much as I want this to go back to normal, I'd hate to give 2oz of watered down prune juice TWICE A DAY if the apple juice even do this.

What do you think?