Panic Attacks - How Does It Feel(?)

I have experienced panic attacks before, but after my mental breakdown, I get them a lot. My friend and neighbor has seen me have panic attacks several times. I think it scared her a lot the first time she saw it, and I wonder, if people in general know, how awful it is - how it feels...
Perhaps its different from person to person, I can only TRY to describe, how it feels for me. To describe it is actually difficult, since the fear takes full control of my mind and body, and I'm not totally aware of my condition in the moment, but here goes...

I feel I cant breathe, like an elephant was sitting on my chest.
My heart is pounding so hard, that I think it will explode or jump out of my body.
I shake all over my body, the fear is incredible.
I want to run away, but there's nowhere to run.
Most often, I feel like vomiting, but not always. And that's usually "after" the attack, or in the end of it.
It's so painful. I have given birth to 2 wonderful children, but there's no comparison to that. I can't tell you, where it hurts. Just that it hurts, and the pain is incredible.
I want to scream out loud, but at the same time my body wants to crumble together - locked somehow. I get the desire to smash my head or my fist into a wall... Just to make the pain go away...! 

Experiencing a panic attack has been said to be one of the most intensely frightening, upsetting and uncomfortable experiences of a person's life. (http://en.wikipedia.org/wiki/Panic_attack)

Well, wikipedia has a description of a panic attack, some of it I have quoted above. I can only second that!

Since I experience panic attacks often, I know what it is, and I am able to (somewhat) during the attack, to realize, what is going on. However its equally frightening each time, and during a panic attack I will do anything to make the pain go away.

Looking at it from an "outside" view it can seem insane to want to smash your head into a wall, to make the pain go away! All I can tell you is, that I agree! That sounds insane from an outside view, because that would only cause more pain to the body.
However, during a panic attack, I really am in panic! It's so difficult to describe, but I have tried anyway. The desire to smash my head or fist into a wall, to cut myself, to do something painful to my body..... It comes from panic attacks being so painful in itself, that channeling the pain into something else - like physical pain - seems to be the only "way out".