How do i know if my mind is playing tricks on me or i am actually seeing things.?

well it sounds like you are actually seeing things...i am christian too and i definatly believe in bad spirits, i sometimes see things at the corners of my eye and i used to be TERRIFIED of my sisters room, i had a HORRIBLE feeling everytime i went in there, i felt watched..i just started praying a lot for help and eventually it got better..be careful of what goes on in your home, dont let your family watch, listen, or do bad things because that could bring in demons..