I have first degree AV block forever, with a pr interval about the same as yours, just ever so slightly outside the normal range--and I have no symptoms and need no treatment. This is the usual thing with first degree heart block.
Medically, it is a very mild condition, so close to normal that it's pretty darn normal. It is not dangerous and it usually does not cause symptoms or need any treatment at all. That is why your doctors are not concerned.
It will probably help you to read about first degree heart block:
http://www.nhlbi.nih.gov/health//dci/Diseases/hb/hb_types.html
So, if your heart is healthy (and repeated testing has shown that it is), what is causing your symptoms?
Check out the symptoms listed here and see if you have experienced any of them:
http://www.helpguide.org/mental/panic_disorder_anxiety_attack_symptom_treatment.htm
You might want to try posting in this medhelp forum, to compare notes with others:
http://www.medhelp.org/forums/Anxiety/show/71