I'm Under A Lot Of Stress And Have Been For

I'm under a lot of stress and have been for a couple of months,last few days the middle of my chest been hurting. Other night I called 911 cause it felt like I couldn't breathe. They checked my oxygen and ekg and blood pressure and said my heart beating normal rate,oxygen is fine and blood pressure is normal.. they believe it was a panic attack.what could be wrong?? I need help