How to diagnose stomach cramps with vomitting and fever

According to the symptoms you report (nausea, vomiting, high fevers, chest pain, severe stomach cramping-left side near belly button, extreme fatigue, and excessive urination) your boyfriend is probably experiencing an infection but I can’t be sure about the location of the infection. Several medical investigations can be done to find out the infection origin:
1. A physical examination (inspection, palpation, auscultation, percussion)
2. Complete blood/urine work (blood count, sedimentation, liver and renal status, urinary sediment…);
3. Abdominal ultrasound, and
4. Abdominal and chest X-ray (if necessary).
You can go to a primary health doctor first and to an internist later, if necessary.