Hi Im 22- I too have this and have only met one other person with the same thing we all have, I have done a Lil bit of looking a around and this is what I found.
It is called mirror movement, The symptoms of mirror movement disorder are pretty much what the name implies. When a person with this disorder moves his right hand, his left hand mirrors the movement, carrying out the same motion (though usually to a lesser extent) as the intended hand. This behavior is often present in babies and in children up to 10 years of age, but once hemisphere-specific motor movements have developed, mirror movement is only seen in people with neurological disorders or deficits. People with mirror movement disorder have reported difficulty in playing the piano, typing and other instances in which each hand must do something completely different from the other.