Question
My upper back vertebrae are CONSTANTLY popping.  It's really painful. If I just arch my back a little it will pop, and it often does this without my even trying.  It often hurts or bugs me because it feels like it needs to pop, but then once it does it just aches and doesn't feel relieved. This goes on literally every 3 minutes.  Sometimes its worse than others. its worse when im sitting or driving more often. Maybe it has to do with bad posture? Also I had a stress fracture in my L5 about 4 years ago from sports overuse, so I don't know if that could have something to do with it.

Answer
First, I would like to apologize for the lateness of my reply.  The holiday has me backed up!!!
You may have a little bit of muscle weakness in the upper back area, causing you to have some instability.  A good chiropractor should be able to asses it and treat it, and to set you up in a good rehab program to strengthen it.