Yes, I have this and I sympathise - it is deeply unpleasant, frightening and something I wouldn't wish on anyone.
I also have very disturbing dreams, in fact I'd say all my dreams were negative in emotional tone, with 90% being nightmares. Again, not nice.
firstly, go and try to get a proper sleep assessment. In this they will hook you up to various monitors and record your brainwaves and certain muscle actions overnight. This can rule out some physical causes of what you're experiencing. I'd also suggest keeping your bedroom cold.
Secondly, this may sound odd, but you can train yourself to realise when you're dreaming. Do you have any recurring imagery in your dreams? If you do, make yourself visualise that several times a day, then link that with a 'reality test.' This is where you stop what you're doing, look around you and think, am I dreaming? For me, I try to concentrate hard on written text. If it shifts, I know I'm dreaming. This isn't easy to do and it takes a long time - it took me a couple of years to get good at it, but it does work. Once you know you're dreaming you can either wake yourself up or control the dream. Google lucid dreaming - I've never managed to turn a bad dream into a long fun one, but just being able to wake was my aim.
Onto the sleep paralysis. This is slightly different, but they think it's basically that you're dreaming, paralysed, but partially awake, so I think of it as the dream overlaid on the real environment. Something to do with the reticular formation in the brain acting up. Anyway, again, if you get good at the knowing you're dreaming technique, you CAN interrupt these episodes.
Mine have ranged from being asleep, and feeling something sitting either on me or on the bed next to me. Not nice when you're in the house alone, or to things stood by the bed, the bed filled with spiders etc. it's absolutely a real feeling.
I read up about this phenomenon, and it occurs in all cultures around the world. It's responsible for many cultural ideas, from night hags who sit on your chest and throttle you, to bad spirits, to alien abduction. Actually it's pretty fascinating!
I've now got mine mainly under control. This wasn't an easy or fast process, but I'd say nine times out of ten, I can now realise I'm dreaming and wake myself. The first thing is to get good at the knowing you're dreaming technique, and the second is to break the paralysis. Weird as it sounds, when I realise this is happening, I try to tell myself it's not real and wiggle my toes. For some reason, I can't move the rest of me but I can often move a toe - this wakes me and breaks it.
Good luck to you. This is a very frightening thing to have happen to you.