Lots of talk about spirit possession. There are two types, demonic possession like the exorcist and possession by "the unquiet dead" as Dr. Edith Fiore talks about. As to the first category, find a priest. As to the second, you can clear your aura of unwanted entities and energetic imprints. The Unquiet Dead by Dr. Fiore is a great resouce.
There is a much faster way that I have developed called Extreme Empowerment. Using the sound of my voice, you listen and together we find and clean all unwanted entities. If interested check out the following: auracleaning.com