I am curious why you are wanting to make the switch now, especially considering your son has had stomach problems. Is this something that you have discussed with your son's pediatrician? The American Academy of Pediatrics does not recommend milk prior to age one. There are two primary reasons for this recommendation: allergies and iron- deficiency anemia. The intestinal lining of a baby is slow to mature and most babies babies simply cannot digest cow's milk yet. If you give your child milk too early, many babies will develop diarrhea, bloating, and abdominal pain, because of their inability to digest the lactose sugar in milk. Also, the allergic proteins may seep through the irritated intestinal lining into the bloodstream and cause an allergic reaction, such as a runny nose, wheezing, or a red, raised, sandpaper-like rash, especially on the cheeks. Some babies who are allergic to cow's milk can even get frequent ear infections.
Iron-deficiency anemia is another problem, as there is very little iron in cow's milk. If baby is allergic to the cow's milk protein, the irritated intestines may consistently lose a tiny bit of blood into baby's stools.
If you haven't already done so, I would highly recommend checking with your pediatrician before starting this too early.
