My 10 year old son missed a lot of school this past school year because of debilitating stomach aches. We had him tested by my Naturopath and come to find out his steatocrit levels where extremely high- he was no processing fats correctly. He loved high fat meals, eating eggs, bacon, toast with more butter than bread- and b/c I'm a WAPF member I'm all about healthy fat! Now, he takes a digestive enzyme called "cholacol" made by standard process with all of his meals. It's made the stomach aches go away and if he forgets to take it he notices the difference.
Stomach aches are a tough one for sure.