What Are The Sudden Episodes Of Severe Labor Pain?

My son, student, 15 years old, has been hospitalises 8 times in the past two years with what I can only describe as a severe sudden onset of labour pains. Last night they dosed him up with 37mg of morphine and it did nothing, he was still screaming in agony for hours. In past 12 months Gallstones rules out, appendix taken out, they have performed cat scans, ultrasounds and every blood test under the sun. Today they administered dye and he had a gastointestial xray which also showed up nothing. During the surgery to remove his appendix they noticed he has a large piece of redundant bowel but now the doctor thinks this is not an issue. Tomorrow he will be finally seen by a gastrointerologist. Can you give me any clues as to what I could ask the specialist to look for, or what further specialist tests could be performed? The only common denominator surrounding each episode is stress, I have no doubt that stress trigers it, but it is clearly a phsiological issues. Do you have any clues or suggestions ?