This is a very weird disorder you have. Are you seeing a psychiatrist or psychologist? I doubt this is anything harmful though; you're not going to grow up to become a criminal. Many serial killers hurt small animals as kids, but not everyone who does it grows up to be a murderer. I'd just suggest that you go see a psychologist and tell him about your fetish for eating wood. It's nothing serious in my opinion though, so don't worry about it too much.
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I worship the power of these lovely two,
With that adoring love known to so few.
'Tis indeed a miracle, one must feel
That two such heavenly creatures are real.