A stomach ache is cramps or a dull ache in the tummy (abdomen). It usually does not last long and is often not serious. Severe abdominal pain is a greater cause for concern. If your stomach cramps have started recently and you also have diarrhoea, the cause may be a tummy bug (gastroenteritis). This means you have a viral or bacterial infection of the stomach and bowel. It should get better without treatment after a few days. Sudden agonising pain in a particular area of your abdomen may be a sign of a serious problem. It could rapidly get worse without treatment.