Hi. Thanks for your query. Noted the history about your son and understood your concerns. Upset stomach, tiredness, dizziness, feeling like throwing up after food can be due to the following reasons: Subclinical intestinal infection or typhoid or so. This can be diagnosed by the following ways: Get a clinical evaluation, examination by a Family Doctor to get a probable diagnosis and to get investigations of stool and blood. A course of an antibiotic, metronidazole if indicated. Activated charcoal tablets, probiotics and multivitamins help early recovery. Gie only boiled and cooled water and homemade fresh foods. Symptomatic additional treatment with Omeprazole, domperidone may help further. These may be sufficient measures to get a relief but if there is no further and complete improvement, second opinion of another Doctor or reference for a Gastroenterologist with additional tests, proper diagnosis and further management can help him the most.