Hi Emma -
Did you know that every night when we dream (usually we have four to five periods of dreaming per night) our bodies temporarily become paralyzed? It's true! That's why you sometimes dream you can't scream or move - because you can't!
If our bodies weren't paralyzed during REM sleep, think of what would happen! We'd get out of bed, run around the house - we might even start "flapping our wings" and try to fly! Does this sound like very restful sleep??
Next time you have one of these "screaming dreams" - try to remember that you - because you can't move - you must be dreaming. Once you realize you're dreaming - try changing the dream to a better ending. If someone's attacking you and you can't get away - remember that you're dreaming and fly off into the sky. If someone's getting too close and you find you can't scream - remember you're dreaming and tell them calmly to get out of your dream. One more thing to remember: You can always wake yourself up from a bad dream - just by opening your eyes!