What can it be?

Bobbie

OK momma's I'm in need of answers or some suggestions at least... My son is almost 14 months old and has had constipation from week 1. When I say constipation I mean absolutely going maybe if lucky 2 times out of 7 days... When he goes you can't even smash it while holding the diaper... There is blood that's red but it's from tearing no internal bleeding is found (he's been in n out of emergency rooms with tests) he's been to one GI doctor and all they did is an upper GI x-ray series with barium which showed nothing out of the ordinary.. My gut feeling that there is an issue lying in the lower GI track but has never had any tests. He eats a high fiber diet including fiber gummies. He's been prescribed miralax and it does absolutely nothing (he's been on adult dosage recommended by GI doctor). He fluctuates in weight exceedingly. I'm just needing help. Ideas. Maybe a mom that has gone through this? What can it be?? It rips at my heart knowing he's in constant discomfort .