meg I'm not sure what I think about 'spirits' but lots of people believe in them and claim to see them.
I've also never hallucinated, so I don't know if what you're experiencing can be described as a normal hallucination. Maybe somebody can explain their own to you and see if this could be that.
Are you on any meds that could be causing hallucinations? Or particularly stressed out right now? I mean, do you feel as though you might be hallucinating?

My ex-best friend's family all claimed to see spirits sometimes, I'm not sure I believe, but I also think it's not possible they were all hallucinating (they didn't even have anything 'wrong' with them), so either they saw them, or they lied. Not sure if that helps you at all but...

Are you in therapy? It might help to talk about it, or to a doctor. They would probably think it's a hallucination I guess, and if it is I guess something needs to be done.
Hope you are ok x