My experience of SP has been like Ummm's, with the sense of something harmful and evil crossing the room towards me and I'm unable to move. Quite often I see a shadowy human figure. I am totally unable to move. But I usually wake up before it gets to me.
I've never experienced the visceral buzzing, though, and I suspect it is to do with you being under unusual stress, so maybe trying some sort of relaxation/meditation class might help.
I've heard that the being pinned down sensation is very common and is one of the origins of the term Night Mare, a hag-like figure that sits on top of the sufferer. Here's an interesting link I was looking at a couple of weeks back with some explanations and suggestions.
http://www.world-of-l.../sleep-paralysis.html
Hope it stops soon. There's nothing worse than disrupted sleep. x