our foster son had this, it is not something that can be fixed quickly. it took us well over two years.
he was on movicol. worked up to two adult doses. Still no luck.
it was suggested he may need to be sent to hospital so they could do a flush out of his bowels.
So the doctor prescribed the bowel cleanse that you take for a colonoscopy We had t do that over three days .
First day he took it nothing. we were disappointed as the doctor had said he would put him on the adult strength to start with.
w e went the second day . still nothing, and my boy who was 9 at the time thought he was being starved cause he was only on clear foods, ie jelly, broth, and drinks.
We called the doctor and said so far we have had nothing not even a small one should we stop and just admit him. He said look lets give it one last try give him double, the adult and if that does nothing then we will admit him.
So we gave him the double does and waited. Nothing that night.
next day we sent him to the toilet, cause even though he wasnt going we still toilet timed and all the rest of it. then it would have been about 11 the next day and we were all prepared to organise hospital cause he didnt even get wind.
This might be too much info for some so be warned
anyhow we sent him to the loo, nothing, we said c'mon mate before you hop off we would like you to take three deep breaths and give a push. OMG, to this day, and ive worked in medical situations for close to 25 years and i never heard or seen anything like it. He was so shocked he yelled out 'mum i did a poo" but he emptied his entire bowel. it was unbelievable.
however after he had emptied we had to keep up with the movicol while his bowels muscles rested and relearned what they had to do. It was a further 6 months before we started reducing the movicol
dose then the frequency in which we gave it. To eventually he might have 1 every couple of months just for a little clean out.
Go back to the doctor and chart a plan of action but be prepared for it too take a while, specially since he has had it for a couple of years.