Talk to Pediatrician on Repeat Constipation

My son is 3 years old. He is having problem with repeat constipation. We are consulting with pediatrician. Mostly dealing it with diet control and medicines i.e. Lactulose ( Duphalac) and Laxatives ( Laxoberon ). Furthermore we have to use Enemas sometimes because he feels pressure for stool but unable to pass it. I have also attached stool tests which are normal. I am looking for remedies or ways to manage this. Ideally also want to know best possible specialists in this regards in Lahore.