thanks for all your advise.
Give him a little prune juice every day and more fiber in his diet and if you have to give him a child's suppository,
how old is your son? You can now get 'omega-3' oil which is basically cod liver oil with additives for more effectiveness and lemon meringue or other sweet flavors. A tsp a day would make his bowels more more smoothly and less painfully. What does the doctor say?
It is a viscious cycle. He won't go because it hurts and because he doesn't go it hurts when he does go. Definitely talk to your pediatrician to find out what you can do. It will take him a few times to realize that it doesn't hurt before the anxiety about pooping goes away. My son did the same thing.
i would try giving him a little bit of stool softner that would help alot and if you havent already i would recommend taking him to the doctor and see if they will prescribe something that will help in a long term effect