Okay, after watching the clip, there are a few differences to my idea afterall, so I;m not going back to the drawing board just yet.
Awesome job btw. You should use the voice modulation more, it really adds to the effect and gives weight to the belief that you were possessed. Suspension of disbelief goes a long way and you nailed it ( Pun may, or may not be intended >.> ) with this one. It's just a pity that you didn't have another actress to work with for reaction shots.