Constant Chest Tightness

Please take time to read my post. thanks.

For the past year i have been have chest tightness, until about  two months ago i started to get the chest pain everyday all day. I am 22yrs old 5'8 205 pounds, I exercise often(walking, occasional run, basketball), I eat good healthy foods most of the time, and Im in pretty good shape. I was however a heavy drug user for 5 years, smoked, drank, pills, narcotics. I quit smoking a couple of months ago and I no longer do any drugs, and i drink in moderation from time to time. So Last december when the chest tightness first came, I paniced and went to the hospital, they took blood tests, and diagnosed me with Gastritis and peptic ulcers. I went on couple of months with the tightness comin and going. I however in august began getting the tightness bad everyday, sometimes felt squeezing, pressure all in my Left Chest under my Left Breast. I went to the ER one day cause during work i began getting the squeezing tightness feeling, I thought i was gonna have a heart attack. They took EKG and Chest Xrays, both normal. They gave me a Vikoden for the pain and it went away for a couple of hours.  A week later from that I went back to the ER for the same reason, Doc did EKG again and it was normal, this time i was diagnosed with Anxeity and panic disorder. Now ever since then I get chest tightness everyday and it varies. The only things that releives the Tightness is Sleep, and Heavy Exercise(running, lifting weights) But maybe and hour or two after the tightness comes back. I also sometimes get tightness in middle of my stomach. I am now starting to worry a bit.  The tightness feeling gives me anxiety. Im fine when i dont feel it. I dont know what starts it.  I am now reading that tightness is a good indicator of Heart Disease. I have insurance but is only accepted in ER's. PLZ someone offer me some good information. Thank you