HI, my son is 17, has had issues with constipation , has increased fiber in his diet, takes miralax every night, and now his pain in the left side of his back and radiating down to his left testicle is so bad, he can barely walk. NO fever, very tired, and in a lot of pain. Motrin doesnt help. He tried milk of mag and all he got was pure liquid stools , and pain continues. now after last night dose of miralax , he had rabbit pellets he said, is it possible he could have an obstruction?