I have had sleep paralysis for many years, haven't had an "episode" in at least 3 years though.

It really is terrifying! You can do some research and find that there are a few scientific explanations. Also, people over the centuries have reported this, it's known as the old hag.

I haven't read through thread yet, I am sure you will get very informative replies. I have learned to remain calm when evil entity is holding me down...once it was growling and speaking in a language unknown to me, I thought for sure it was going to kill me.