Evil entity in me?

For a long time I have experienced intruder negative thoughts like, for example, if someone is near a cliff I imagine pushing him/her (all in my imagination and I never consider actually doing sth like that). Nevertheless I'm very sane and functional and I kind of got used to this thoughts to the point I dont pay them atention as disturbing as they may seem to another person. Im a very positive and peaceful guy and I keep my self in the light and Im recieving lots of help. However after reading Evolution by Bruce I started to consider that may be I have an evil entity attached that is causing me this thoughts. Today after reading a post on shielding I read about placing a mark where I sleep, they mentioned a cross. I tried to visualize one and inmediately I imagined the upside down cross. Moment later I felt a negative energy coming from me wich I've felt many times before, it feels like an evil energy and it makes my heart race and feels unnatural. I wonder if I did "dark magic" or something. I cant seem to visualize anything but negative stuff like the example above when I tried to visualize the cross.
Is there any way I can get rid of this thoughts or if I have an evil entity attached get rid of it?