| When I don't get enough sleep for a long enough period of time I REM while I am awake. Usually this happens exactly as you described, but also occasionally when I have been awake for hours. As long as I get enough sleep then I never see anything that isn't there.
I have a SIL who works in a sleep study environment and she has a patient who REMs awake all the time. She'll wake up to use the washroom and the dreams continue all around her to the point that she can't turn on the light because they get worse instead of going away.
If you go to the doctor and tell them about your hallucinations they'll send you for tests to determine why they are happening and how to stop it. | 
