Yep, that’s sleep paralysis. It’s very creepy. Here is an excellent website discussing the matter:
I’ve lucid dreamed a couple of times – the best was several years back, where I realized I was asleep, and went “flying” in my dream 
By the way, sorta OT…my mom used to have some problems sleeping, so her doctor gave her some new pills to try out. She took 'em, they knocked her out, and when she woke up she was having an out-of-body experience. She said she could see herself walking around, like “she” was hovering about a foot over “her” head. Whigged her out, so she laid back down, and managed to fall back asleep. When she woke up, she was back in her body, and disposed of those pills pretty damn quick. Does anybody know what could have triggered this?
I have occasionally had lucid dreams. In one I decided to deliberately study the sense-qualities of the objects around me. I remember running my hand over a brick wall. It did indeed have a rough texture rather like brick, yet the intensity seemed muted…like a false substitute that is only acceptable if you don’t look too closely.
I also performed some other experiments, which I am loathe to describe. But the conclusion was the same.
I have lucid dreams about 3 times a month on average. About half the time I wake up when I realize that I’m dreaming. If I manage to stay asleep, I will either fly (by pushing imaginary energy out the palms of my hands) or have sex with the nearest attractive woman. If I’m not sure wether or not I’m dreaming, I will try to fly. Fortunately I haven’t tried to fly while awake yet.
Rather OT, but I used to do drugs too and decided that if I ever thought I could fly on halucinogens, I would not jump off anything higher than a curb.
Add me to the group who have gotten way fucking high in dreams. Kinda scary my first couple years in 12-step recovery, but now I take it as a certain sign that I’m dreaming; kinda like going to school in your underwear
That’s called a false awakening. I’ve had a series of 4 once (i.e. I wake up, then I wake up again, then I wake up again) - and after each one I said “shoot, I guess there is a reason I’m supposed to check reality each time I wake up”
I lucid dream on demand; and what’s REALLY the best thing to do is talk to dream characters. Reason with the unreasonable; it’s a lot more fun (and easier to sustain while asleep) than say, sex.
I lucid dream a lot: I had no idea it was common.
Often I will correct the dream: if something has happened that was impossible, then my brain will force the dream back and re-do that part of the “plot”.
More frustrating is that often I don’t remember my dreams, but my dreaming mind remembers my dreams. If I’m in a lucid dream , I question that memory, and then work out that its from a dream I haven’t remembered consciously.
I could write a book on this. I have severe insomnia, and often dream that I am in bed trying to fall asleep. I eventually realized this, and decided to see if I could make something happen. The first time I tried, I was dreaming I was trying to fall asleep on my stomach, I turned over and someone dived right into my stomach.
Since then, while dreaming I am lying in bed trying to fall asleep, I have been shot several times (once, after dental surgery, my sister came into the room and shot the back of my neck, and all my teeth fell out), had boiling water poured on me (it was summer and hot) and a bunch of other stuff. I’ll never forget the morning of August 31, 1997 when I dreamed I was in bed and a big black train came through a tunnel and rolled over me. I had been listening to Starlight Express before going to bed (There’s a light at the end of the tunnel) and decided that was why. Then I got up, turned on the news, and heard about Princess Diana’s death! Weird, huh?
Cecil addressed the phenomenon of sleep paralysis here.
Cecil also tangentially addressed the phenomenon here.
Oops. That was Straight Dope staffer Doug who wrote that last entry linked above. Credit where credit is due.