B.H.
Mirlax is what the doctor's subscribed for my son. You can now buy it over the counter. 1/2 to one cap full a day mixed in his orange juice every morning. Mirlax prevents hard stools and constipation. It can be used for an entire year without worries as it is not a laxitive.
My son did not want to go either so I would give him a prize after each time he went. I went to the dollar store and picked up some toys to use as the prizes. We called them pooping prizes. Good luck and keep a close eye on this as you do not want it to develop into something worst. Because it can.