Pain above stomach, below rib cage

Hi,  my 14 year old son has been having problems with his stomach for years. He's been for all sorts of testing and they can't seem to find anything wrong.  This has been going on since 5th grade.  
Today for example, he get's this pain above the stomach, but below the ribcage. It hurts so bad that he can't move.
I took him to his doctor and it hurt when he applied pressure but the doctor sent him home. Lungs checked out clear. He didn't know what else to do for him. My son still wants to eat, that's a good thing, but the pain last sometimes for 2 days. I gave him Mylanta, didn't help. Finally sent him to bed with Tylenol. Does anyone have any idea what could be causing this pain so I can research it further?

Thank you