I have burning and stabbing pain in upper abdomen going through to my back. what could this be?

Many reasons: could inflammation of the pancreas or gallbladder... Also could be stomach ulcer or gallbladder stones. See your doctor for exam and appropriate testing.

Pancreatitis?: I would suggest to go to the ER to get checked. Most common cause of pancreatitis is gall-bladder stone or excessive alcohol consumption. They do blood test to check the amylase and lipase level and give you a ct scan of the abdomen. If pancreatitis you may need to be hospitalized.