Hip Pain for 6 plus years

[throwscoach]

I am a former track and field athlete, a thrower to be exact.  I am now 26 years old.  During March of my sophomore year of college (2003), I began having major pain in my left hip flexor.  It was almost constant and the training staff could not determine what was causing the pain.  Then, in July of that year, my hip suddenly "popped" and the pain instantly subsided.  Since that time, anytime the pain returns, I attempt to "pop" it and again the pain is almost immediately gone.  The pain occurs mostly anytime I have long times of hip constriction (sitting at my desk).  Recently, I have been unable to make the hip "pop" and the pain has been almost unbearable.  The pain is now radiating down to the left knee joint.  Heat and/or ice has never really helped this problem at all.  Anybody had any similar problems?  I am up to suggestion for how to "cure" this pain.