If you are getting stomach ache constantly for more than two days, then pay a visit to your doctor now. In case, it is accompanied by symptoms like vomiting, diarrhea, fever, etc., then consult the doctor before the symptoms worsen any further. After physical examination of the abdomen, they can identify the actual reason. Otherwise, some laboratory tests like stool, urine and blood tests, X-rays or ultrasound are conducted to ascertain the cause.