It sounds like a touch of awareness during sleep paralysis. You become aware you are in a dream like state but can't move or in your case can't scream. The light not coming on is something that I have experienced before also. In fact one of the strangest experiences I every had was when I woke up and tried to turn my reading lamp on next to my bed but it didn't come on. I then got out of bed and walked downstairs and over to the front door to turn the dinning room light on and it didn't come on either. I then started to get this real eyrie feeling that I wasn't in Kansas any more. The next thing I know I wake up in my bed. I found out later what I had experienced was called a false awakening which is like a type of OBE. I also found out that sleep paralysis is related to those states or can act as a spring board for such experiences.