I know perfectly well what you are talking about, I too have experienced many times sleep paralysis and it is a terrifying experience. I remember that the first time I experienced it was barely a 20-year-old girl and it scared me so much that I suffered from insomnia because I was afraid of falling asleep. At that time I was taken to a village witch and she said that it was an evil spirit that had fallen in love with me and that she was not going to leave until she got her job! I remember that at that time I read a lot about incubus, a kind of evil demon that sits on top of people while they sleep. Later on, I understood that there was a scientific reason for what I was feeling and that it was what we call sleep paralysis. Although I have time that I don't feel it, thank God, every time I hear about it, a cold air crosses my back.