Terrifying Recurrence

I just remembered these "sensations" I used to get a year back and decided to post here to see what you guys have to say.

Let me explain.

Sometimes when I go to sleep as usual (this is before I found out about LD's), I will suddenly be thrown into this incredibly intense feeling of terror for no reason at all. I can't find any objective impetus to this dread...it just happens, out of the blue.

I used to shake myself out of it, and being bewildered about what just "happened" to me, but I've learned to try to keep the feeling coming to see what happens, and I found some interesting results:

When I start to feel the fear come onto me, my heart rate increases, my breathing becomes heavy, and my chest feels like it's closing in slightly...can't really explain it. Typically, I would open my eyes at this point, but more recently, I just kept my eyes closed and submitted myself to it.

As the fear grew inside me, I feel like I'm sinking into myself; a shrinking feeling. All this reaches a crescendo when the "voices" in my head start talking to me. I can't figure out what they're saying, but I presume this "thing" is trying to make a decision about something it wants to do to me, and when it does, I see an extremely vague image of what looks similar to my monitor's power button and I precede to pushing it myself. Suddenly, everything reaches a crescendo and I explode inside. I feel like I'm shrinking incredibly fast, and I think I hear myself emit this blood-chilling, deafening SCREAM in my head. At this point, the terror is unbearably strong, my muscles tense, my heart jumps over and over, my breathing is deep, I'm shaking all over, I sweat a little, when I stop screaming (usually the scream lasts for what I think is 10-20 seconds), I hear a very high-pitched and "loud" (loud isn't really the word to describe it, I don't know how...don't think in terms of volume), ringing in my head.

Then it just stops.

Everything fades abruptly, fear gone, screaming, just everything, as if it wasn't even there. One thing I also noticed after everything vanished, was BEFORE I moved an inch, my body felt sort of numb...Like, I would think about say my legs, but I couldn't feel the sheets or anything on them, or my chest, and I couldn't feel the shirt I'm wearing. The sense of touch quickly comes back when I move.

Take everything I said seriously; nothing is exaggerated, or fabricated. This might be a real psychological problem or something, so I'd appreciate any theories/comments.

In fact, I had another experience with it 1-2 weeks ago, and it always happens in the order I presented it in.

Some people tell me they've experience something like this before, but not quite like mine.