He was drinking about 16 ozs of milk a day, plus eating fruits and veggies with his lunch/dinner. In the morning he has a wheat-fiber cereal. I do water down his juices half and half. He drinks plenty of juices during the day and we try to make sure he mainly eats healthy foods. My older daughter who is 8 was diagnosed with IBS (irritable bowel syndrome). She also was constipated all the time but i dont think she had such a severe problem with having a bowel movement when she was his age . Her doctor recommeneded organic milk because they put so much in regular milk and to take a fiber supplement (but that was at the age of 7). I just didnt know because of his age, what he is able to have. So we are trying to go without milk for just a week to see if he has any changes and if he does then we can know its the milk. If it doesnt resolve or get better we know its so much more. But I will be taking him to the doctors to see what they say. I wanted to see if there were any other parents out there that may be or have experienced the same problem with their young one. My mom also has done foster care and she had many infants with the exact same problem they did have to drink lactose milk because their bodies just couldnt handle the regular cows milk. One of the kids (which she adopted) has to take mirolax but again her daughter is 7 not 15 months, Thank you so much for your advice it was muchly appreciated.
Generally if a child is lactose intolerant they would have diarrhoea rather than constipation, but constipation is quite common in formula fed infants. Your mum is right - if he was sensitive to the lactose in normal formula, he would also be sensitive to cow's milk, but I would doubt that the milk is his problem. Does he drink things other than milk? Will he take water or watered down fruit juice for example? How is his diet generally? Does he have plenty of fruit and vegetables, fibre from brown bread or brown pasta? You could try giving him something like bran flakes for his breakfast in the morning, but you need to make sure he's drinking a lot as well - if he gets lots of fibre but not enough fluid, it will actually make things worse.
You should talk to his doctor about some treatment for his constipation, there are plenty of medications out there that you could try to help your son.