Hey Jimbo!
I've had this for about 12 years now and I've always had dizzy spells, lightheadedness, unreality feelings and get very tired. I think it comes from the fact that emotions take a toll on us physically and it wears us down. I found out yesterday that I have become anemic from an excessive menstrual problem I've been dealing with but because the symptoms of anemia (dizzy, tired, weak, etc....) are so close to what I've always been feeling with the panic / anxiety, I never thought there could be a physical aspect to it. Have you thought about getting your iron levels checked?
It really stinks that so many of our panic symptoms are the same symptoms of actual physical problems! I always wonder how I will ever be able to tell if there's something really wrong or if it's just more panic symptoms. ARGH