Hi, my gal who is 5 year old has this problem too since baby. I have been bringing her to see KKH specialist for several visit and not much improve, therefore, I tried several method, like give her prebiotics gummy bear, more vegetables and fruits, and drink more water. I used therapeutic grade essential oils from Young Living to massage her tummy clockwise and supplement c.
Now it improve a lot... from poo every 1.5 week or less to now every week. I cut down her FM to 2 twice a day, you can give goat fm as it is more easier to digest.
There is no any method which can cure her this problem, I just able to smoothe her pain when she trying hard to poo out.
Hope this help you.