Could you be lactose intolerant ? My DD is. We found this out a few months ago when she was coming home ever day with her stomach inside out. We cut out milk and cheese for a few days and poof.. gone. I started her on Lactose Free milk (which is really good btw) and she does wonderful on it.
I am learning more and more about lactose free diet... she can eat mozzarella cheese (pizza) and hard cheeses but softer cheeses have the sugars that upsets her stomach.
FORGET ice cream... its a killer.