Dizzy and faint - anxiety symptoms ?

I am a 25 year old female. Healthy my whole life, normal weight range, have one 3 year old son. For 2 years now I have been experiencing these weird symptoms. It happened out of nowhere one night for the first time while I was just laying down watching TV. I had just had an abnormal pap smear and had to go back for further testing which came back negative. I experienced a strange sensation in my arm. Like needles poking. Then I stood up and felt dizzy and faint. I called my sister who lived with me at the time and she called an ambulance. I thought I was dying. They took my BP which was high but going down by the minute. They said I was having a panic attack and no need to go to the ER.

Well ever since that day I have been having "episodes" of these symptoms. Some days I am 100 percent fine. No symptoms at all. I can go with no symptoms for weeks even a few months and I will think they are never coming back. But then out of no where again, the symptoms come back and they last for days or sometimes WEEKS.

Here are my symptoms:
-Weird headaches like a pressure or my head feels like it's going to blow up.
-weird chest pains. sometimes shooting pains sometimes a dull achy pain.
-feeling of "out of my body" like I'm not me or like I'm somewhere else
-dizziness
-fatigue
-shortness of breath. I feel like i have to breathe deeply to get air.
-just a strange panic like feeling. like i'm dying at any minute.
-a "jittery" feeling all over my body. Sometimes you can even see my hands shaking.

Now when the symptoms are not there, I don't feel the anxiety. I have been to MANY doctors. All say it's anxiety. I have tried several medications. xanex is all that seems to help but only for a short time and the symptoms come back. I have been to a cardiologist, a neurologist, and my regular doctor. Not to mention the many times my husband has taken me to the ER for this. And had many tests including blood work, CAT scan, MRI, Chest xrays, ekgs, etc. NOTHING has shown in any tests that there is anything at all wrong with me. All my docs say I'm perfectly healthy and these symptoms are simply anxiety and panic related and i need to calm down. Well its hard to calm down when I feel like I'm dying. So basically I'm not sure if the symptoms are causing the anxiety or the anxiety is causing the symptoms. I am scared to death that I have a horrible physical problem no doctor has discovered yet and that I will die if I continue on this way. Are all these symptoms "normal" for just an anxiety disorder? And if not, why are all my tests and doctors saying I'm healthy? The symptoms seem to have no rhyme or reason. They come and go. I am so tired of this. PLEASE help me!