What can cause abdominal pain, loss of appetite, vomiting, and weight loss and can come and go for months?

It has been going on for at least 6 or 8 months. It will last for a few weeks, then go away for a few days or weeks and come back. All of the symptoms are the abdominal pain in the upper part of the abdomen, loss of appetite, vomiting, severe fatigue, and weight loss. I am really scared for my girlfriend, as we do not have insurance nor enough money for a doctor… please help.