The fact that you have panic disorder is the key here. If you had chest pain and didn't suffer from anxiety attacks or any prior cardiac problems and you received a normal EKG, that wouldn't eliminate the problem entirely. However, panic disorder can mimic symptoms of a heart attack. Sometimes during a panic attack, the victim not only will have chest pain but numbness in the left arm and radiating pain!
This is why I'm pretty sure you're okay, especially since your EKG results are normal. I realize that faulty thinking in anxiety disorders, such as "My heart's beating fast- I must be having a heart attack!" can be hard to overcome, but I think that I can safely say that the panic disorder is the real problem here...
I do agree though that, if you truly believe that the problem isn't caused by panic disorder, that you should get a second opinion just to be on the safe side .Remember what I told you on the panic disorder board- the disease just wants you to fall into its trap. Don't let it! Good luck and God bless!