Freshman psych class taught me that eyewitness testimony is among the most unreliable forms of evidence around. My psych teacher would get out of jury duty every time just by saying he's a psychologist whose research focuses on the unreliability of eyewitness testimony.
Just because you experience something doesn't mean you're qualified to interpret the experience.
That said, just because something happens in your head doesn't mean it isn't real.
But what does "real" mean? There is no evidence for actual invisible beings walking around our planet nor is there any testable hypothesis I know of for how such an invisible being could even be possible. (If there is, I think that would be cool to read about, so post a link. )