How is a Demon this powerful destroyed?

My life has been taken over by this terrible entity. The power in it is incredibly strong and it wants to kill my 2 year old daughter the obsession it has in her is terrifying to me. We left a recorder on at night and we saw it in the form of a shadow leaning over her crib and calling her name in an altered, sadastic, non human voice and then it slapped the camcorder off of the night stand. I am not a believer in any god, but I do believe in the supernataural world so I have no idea what to do, I am on th brink of utter insanity.