^ i think ive heard something about this sleep paralysis thing before, although im not quite sure. from what i remember its caused by a chemical thats released to the body (or the brain, cant remember long time ago) that relaxs it and 'puts it to sleep', so to say. the problem arises when the brain wakes up but the body reacted slower, meaning the mind realises the paralysis and causes you to panic. i remember reading someone on another forum writing about it a few years ago.
http://en.wikipedia.org/wiki/REM_atonia#Physiology_of_REM_sleep
i looked it up and aparantly it is similar to REM atonia, another form of paralysis in which the body emits a chemical compound to submit the muscles so they dont work during the night. interesting stuff, although i cant remember if ive ever experienced it. the only real thing that has happened to me related to paralysis is sleeping on my hand and then being unable to move it in the morning lol, had to shake it and rub it until blood re entered
although you said you cant breathe at all which is strange...the stuff i was talking about apparantly doesnt restrict oxygen intake because its a natural occurence during sleepytime