Suggest Treatment For Severe Constipation In A Child

My 2 year old son gets constipated a lot, he pushes for days and days(he hadn t gone in 5 days, so I gave him a suppository) he finally had 2 hard pieces of stool come out hours after the suppository and they smelled strongly of ammonia. This isn t the first time it s smelled like that. I give him cuterelle probiotics almost everyday and that doesn t seem to help, also prune juice, pear juice, plain water, nothing seems to keep him regular. I m wondering if I need to take him to the dr or a gi?!