Since your son's vomiting returned after taking Domstal (domperidone), it is important to have him evaluated by a pediatrician. To find the cause, the doctor might recommend an abdominal ultrasound to check his tummy, alongside simple blood or urine tests to rule out infections. Yes, headaches combined with stomach aches and vomiting can sometimes indicate childhood migraines (or abdominal migraines). Please ensure he stays hydrated with small, frequent sips of electrolyte solutions and visit his pediatrician soon for a proper physical examination and tailored guidance.