The other causes could be jaundice if there is yellowish discoloration of skin,
food poisoning if the symptoms occurred shortly after taking
food, peptic ulcer disease and sometimes cholecystitis and pancreatitis.
Headache may/may not be related to the stomach ache. Common viruses that cause cold flu or stomach flu can cause nausea and headache. There may be other associated signs like runny nose, diarrhea, fever, body aches which may be suggestive of a viral illness.