ViolinAddict,
Have you had your thyroid checked? Sometimes it's overlooked by doctors where I live.

Anyway... There are lots of different ways that anxiety disorders can manifest themselves. I get panic attacks from time to time. Often totally spontaneous. They come in bouts and then I can go for a year or more and everything is fine. My main physical symptoms include a type of aura prior to the attack, where my surroundings seem a little unreal. I become extra aware of my surroundings... sounds get more intense, lighting seems too bright. My breathing changes. The palms of my hands perspire. Usually I feel as if I'm going to die. Fortunately I have a pretty good handle on my panic attacks these days and can recognize that I am not going to actually die, although it feels that way.

All the usual fight or flight responses.

There are a number of different Anxiety Disorders.
http://psychcentral.com/disorders/anxiety/
from PsychCentral
Anxiety
An Introduction to Anxiety Disorders
By John M. Grohol, Psy.D.