I have a 3 year old son who has suffered from constipation since he was about 6 months old.That is when he had to go onto formula because I fell pregnant again.Anyway we tried using everything for him.Applesuace, juice's, water giving him lots of fibre and changing his diet.Eventually his ped recommended Miralalx at 1 year old.He was on that for 6 months and then was referred to a G.I. dr .He then put him on a strict diet and a maintenance of Miralax. He was slowly weened off that and was okay for a short while. He then started holding back his poop.It was so traumatic for him and us that we couldn't go anywhere. We then went back to the G.I. dr and he tested his thyroid and celiac which all came our negative.He was then put back on Miralax. I had heard negative things about it so I changed him to Magnesium Sterate.That was working very well until one day he decided to hold back again and really made things bad for himself.He was having severe stomach pains and his personality changed.he became really aggressive and mean towards everyone.He also wanted to sleep all the time to avoid pooping. We called the G.I. dr again and he put him back on the miralax. A whole cap full once a day.He has been on that since last wednesday.He has had 5 bowel movements since then. Does anyone else have any suggestions for me.He does eat a lot of fibre in his diet.We try give him at least 8grms a day.he also has very watered down juice. The Dr talked about a rectal test to measure the pressure in his rectal muscles and also doing a biopsy.Has anyone had this done to their child and do you know what they are looking for?Any input would be appreciated. I am really concerned as we have been dealing with this for a long time. I must say that he holds back whether he is constipated or not.His poop has been really soft the times that he was holding back and he would tell me that it is not even hurting him. The only time that he doesn't complain is when he is having a cap full of Miralax and then it just pours out of him. I would like him to learn to have healthy normal bowel movements. Thanks again in advance.