Well, for a long long while I have been able to see things, like ghosts (they were proved not to be hallucinations). It wasn't too abnormal at first but I think that something might be in me.
Okay so basically sometimes I'll look in the mirror and it will be my reflection but, I have jagged teeth and black eyes and I'm really quite pale. Then I had a dream that I was in a room made of mirrors and that was my reflection in all of them.
Then, in math class, I was getting up to get a piece of scratch paper and when I went to go back to my seat I saw the 'me' with jagged teeth and the such like I had in the mirror. She was sitting there taking the test and was quite translucent. I dropped my paper out of shot and when I picked it back up she was gone, the rest of the time that I was in the seat I felt sick and uneasy.. .
The mirror thing used to happen when I was a child but, I didn't think anything of it.
I swear on my grandfathers grave that all of this actually happened!! I just don't know what that would mean...

If its happening since childhood, you should consult a doctor and share the problem with family.

How were these ghosts "proven" not to be hallucinations?

Also, situations that involve spirit manifestations rarely have meaning to them.