Trying to understand Chest Pains

10 days ago, as I was touring a college I had sharp stabbing pain in my chest.  I couldn't breath and I didn't see myself making up the rest of the stairs.  The next day it happened again all the while there is a constant heaviness on my chest as if someone is sitting on me.  But on occasions; and quite a few thru out the day I have this stabbing feeling.  I hold my chest and wait for it to pass.  I've been to the er they did ct scan, ekg, blood work, xray....all looked good.  They kep me in over night for a stress test the next day.  It also came back good except they said they wished my heart would have squeezed a little more.  Two days later I went to see a heart dr.  Scheduled me for a echocardiogram.  It came back good.  But, I still have these horrible pains and constant heaviness in my chest.  I also have bad headaches.  So today I go see a family dr.  He states it is probably anxiety.  How can that be?  All of a sudden I have stabbing pains in my chest that have lasted for 10 days now?  The only rx I'm taking is an antacid they prescribed and celebrex.  This is not in my head.  I'm an active guy who works outside construction for a living.  I have smoked since I was 13 and I"m 48 now.  I drink a couple of beers a day on a regular basis.  The family dr. took an axiety test and said I failed.  Well yeah, I have anxiety over all this pain I'm feeling with no answers.  Any ideas what this could be? HELP!!!