Is it possible to tell the difference between possible pancreatic pain and stomach or intestine pain?

Yes: Depends on the clinical characteristics of the pain, the physical exam and the levels of certain enzymes in your blood.

With tests by doctor: Even a physican exam by your doctor will be unlikely to differentiate. You will need blood tests and Xrays; sometimes an endoscopy to find the answer.

Yes it is: Beginning with a serious of questions, then a physical examination, then appropriate tests including blood and imaging (ultrasound and CT scans for examples), ad possibly a gastroenterology specialist if needed, your physician will eventually arrive at a solution.