What could this be? :( Scared.

For over 5 years I've had on and off a pain behind my left rib cage.. comes and goes every few months but lasts for many days.I'm 27 years old, male.. I've had uppger G.I.'s done (have been on prevacide for a few years for GERD - i did have tiny tiny ulcers and inflammation of the esophageal bulb), abdominal cat scan that was normal, chest xray, lower g.i.'s, etc...The pain is strange. When it starts, it starts at night time and it occurs throughout the whole day. It seems that it is kind of a radiating pain that radiates throughout my whole left chest - it can happen when I take a breath, or change position, or lay on that side or the opposite side. Usually it helps to just lay flat on my back - but that doesn't always work.After so many years of this when it does happen I get so panicked and frustrated. I worry its some kind of cancer, like its my spleen or something..I've been told maybe spleenic flexure syndrome by some people, or just gas or spasms by others.  I don't know anymore. I'm so afraid.

[DougPoison]

Did any of your tests find or look for hiatal hernia?  I'm not sure if this is the same, but before I had my hiatal hernia repaired, I had a lot of on and off pain in my left chest cavity.  It didn't seem to come from anything special like food or movement either.  That pain wasn't severe or long staying though.  I have GERD, which was mostly caused by my hiatal hernia.  I had surgery, and the GERD is much improved, but not completely.  Prevacid did not help my GERD anywhere close to enough because it didn't seem to stop that pain or my shortness of breath from light exercise.  I'm only 24 now; so I feel for you.  
I may be way off, but it's just a suggestion.  Hope I have helped or someone else can.  Good luck and God bless.