I'm not sure if your son is completely off of breastmilk/formula and getting 100% of his nutrition from milk and food. He's not 1 yr yet, right? Either way, that seems like an awful lot of milk. When we stopped formula and switched to milk and "real food," my Pediatrician told me that my kids should drink no more than 24oz per day (even to their current ages). Also, when I stopped formula and started milk, I eliminated bottles so I didn't contend with bedtime feedings. But, again, my kids were a bit older -- 13 months old or so.
Too much milk causes constipation. But my children have never had this problem, despite the fact that some days they have a bit more than 24 oz. I have them drink water in between meals and try to save the milk (which they love) for meals.
You probably should call your Pediatrician and get some expert advice, based upon your son's food/formula/breastmilk situation.
PS...you didn't mention if you give your son a bottle of milk to take into the crib, but please know that that practice is terrible for a child's teeth.