What Might Cause Severe Stomach Pain, Appetite Loss, Weight Loss,

What might cause severe stomach pain, appetite loss, weight loss, inability to drink water, delusions, paranoia, confusion, weakness. No diarrhea or constipation but infrequent bowel movements. Stomach pain onset ten years ago, first occasional until last 3 months frequent and last two weeks constant. Confusion and paranoia onset 5 days ago. Patient, 54, male, moderate-occasional binge dinner, smoker, auto mechanic. Stopped drinking three weeks ago, continuing to smoke. CT scan with contrast negative. No other test results known at this time. Severe dehydration has put patient in ER three times this week.