Dear Prettyprincess ji,
I can well imagine your suffering. And, agree that in desperation we try to do everything we can. Your situation is really alarming. If you believe it is evil spirit, try taking Udi as Saidasan ji suggested. It has amazing healing powers. Besides, consider visiting Shirdi if you can. In Sai Samadhi Mandir, miracles happen. I also heard that there is a place called Baala ji in Rajasthan which has Hanuman temple where such evil spirits are driven out of people. I haven't visited Baala ji, but some people who have been there confirm that many possessed people get cured there amazingly. Try visiting any or both these sacred places to get well. Our prayers are with you. May Baba cast His healing glance upon you.
Om Sai Ram!