Night terrors, bad dreams, what do they mean?

I'v been having night terrors for a few years now and was wondering if someone could tell me what they mean. I'm going to explain the worst 3.

1) I was in my room (i dont remember what led up to this) but I was tied to my desk chair and gagged on the window side of my room. Someone started cutting into me slowly with a sarated knife across the boney bit at the top of my spine. I could feel each notch of the knife grind across, it was horrible, i remember being scared, when I woke up (in real life) I couldn't move for 20 seconds or so, and i was trying to scream but no noise was coming out.

2) I was working for some kind of strange agency, and I was sent to do some work in an office that belonged to someone else, i remember the office was on the ground floor. While I was in there the building was attacked by another agency (like spy of government) and the room was gassed, I was tied up and shoved under a desk, and semi-consious while people injected me with stuff. I can remember thinking they've got the wrong person. When I woke up I was flustered, and confused.

3) Someone broke into my room at uni and was attacking me, I can't remeber much, but I was dragged across the bed by my leg, and almost as if i was caught between real life and the dream I was reaching for my bedside lamp, I knew i was in a dream and was trying to wake myself up.

Can anyone shed any light on what these mean please?

oh dear this is scary