Hi Penny,
I do hope you find the answers you need soon! I can understand how a mystery symptom causes anxiety! Hibee has advised you well above...so I will just add a link for some great relaxation/stress relieving exercises to try.:)
Self Help sites with breathing/relaxation exercises instructions
Panic attack relief exercises:
http://www.moodjuice.scot.nhs.uk/panic.asp
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
Let us know how everything goes with your tests and search for answers...
...and post with us anytime for anxiety support!
Scaredy Cat