AF,
I don't know if you have ever checked out this site from our Resources or not, but it gives a really good list of the physical symptoms that anxiety can cause.
http://www.anxietycentre.com/anxiety-symptoms.shtml
Since you have checked out allright with the ER and your regular doctors...you can probably be sure that this is anxiety related...or you can keep pursing a medical cause, and ask to see a specialist to help you find the answers.
Either way, I wish you luck and peace!
S.C.
p.s. have you tried doing breathing and relaxation exercises consistently, and did it make any difference in how you feel?