Angina at 25 ?

I am a 25 year old female who is trying to get in shape. I am 5'2", 140 lbs, normal BP and healthy overall. I have been diagnosed with PVCs which drive me nuts at times, but my doctor says they are nothing to worry about. My concern is that I have been experiencing chest pains while exercising (joggging) recently. The pain is high, about two inches below my collarbone, and it is just left of center. It is not severe; it almost feels like a stitch (like the kind you get in your side). It goes away after a few minutes of rest. I have had an ECG, an echo, a CT and an MRI of my chest in the past six months which showed nothing out of the ordinary heart-wise. (Those tests were run due to panic attacks I had during a transition period in my life). Is it likely this pain is angina? I feel very upset; just as I am trying to get in shape, I get discouraged by worries. Would blockages have shown up on one of the tests? Am I getting worked up over nothing, and if so, what is causing this strange sensation? Any help is greatly appreciated.