Creature behind my back

All my life, as much as I remember, I have been seeing things different from others.
I mean, really. Parents and doctor think that it's only my imagination, with which I'm trying to draw attention, it's not true. I know what I see. And about thing like that I would never lie. Almost never.
But my parents don't care. They have their own truth, which is practically impossible to change.
So the only things I have are my diary and my "Dog".
I know Mike for a long time. We first met, when he was five and I was four years old. We were at the beach. He had funny swimming goggles and a little branch in his hand.
And he had a large dog, with big and fluffy tail, behind his back. That's why I call him my "Dog".
At first he didn't believe me, but with time he became used to it. Now, he's only person who really believes me.
He always comforts me, when I'm sad.
Or frightened.
Actually there's only one thing I'm scared. And that's the creature behind me.
Every day, walking through masses of people, sitting at bus stop or just doodling at school, I see hundreds of people. Everyone has their own "pet", how I call them. After look at it you can tell what kind of person is it's "master". Ugly or beautiful, big or small, noisy or silent, they all are different and unique.
And it's also with my one.
That's the reason why I never look at my self in mirror. I'm scared of those eyes. Those empty, black eyes of that thing behind me.
I can't find another way how to describe it.
It's a creature.