C.W.
I am sorry...this is an awful symptom.:(
Spend some time on a few of these exercises. Try a couple out...pick the one that seems best suited...and dedicate some time on practicing it, daily for at least 10 min, 3x's a day if you can. It will help.:)
Self Help sites with breathing/relaxation exercises instructions
Panic attack relief exercises:
http://www.healthcentral.com/anxiety/c/73076/34334/breathing-lessons/
http://www.healthyplace.com/
http://www.stress-relief-exercises.com/
http://www.ehow.com/video_4405003_breathing-exercises-panic-attacks.html
http://www.psybersquare.com/anxiety/panic_relax_I
S.C.