Lisa D/
Take your son to a doctor that specializes in yeast. When my son was in the second grade he also had severe stomach problems. The doctors did all the same tests and we took in lots of stool samples. When I finally took one in myself that was all puffy and looked yeasty, the lab technician said she had mentioned it previously to the MD who just dismissed it. We went to a neighboring city and had him checked for yeast and that was his problem. He recovered fairly promptly, but would still have recurrences when he ate too many sweets or was on antibiotics.