OMG!!!! I have a story (those who know me are now allowed to roll there eyes and say "when doesn't the loser have a story").
So the big ugly kid, who has almost always been bigger and stronger then his classmates, is the same way. I'd be that kid sitting in the back, not talking, just hoping to be ignored. I started doing karate in 6th grade and by eigth I was just anouther outgoing kid. When I did kata, I would redo a move a thousand times if needed to do a technique right. From doing this I became able to learn techniques with ease. I can, to degrees, learn very advanced level moves from haveing them done to me once or twice in a sparring match. I also became able to come with a unique counter to any strategy through my way.
But I still did poorly in sparring. I retreated alot, bent away, looked away, and anything else you think of, and then some. Now I'm in 11th grade, and I'm just now getting over it. I fought like a shy kid for a few reasons. Partly out of fear of getting hurt myself, partly out of fear of hurting my opponent, partly out of still being shy and very none-confrentational. It was a month ago I took a giant step forward, and started to truelly push forward.
The first step, drill techniques, combanations, and kata that don't have retreating components. (builds muscle memory)
If that fails, after every match do 5 push ups for every time you did something bad. (negitive reinforcement)
If that fails, take your self out for a treat every time you do well. (positive reinforcement)
If that fails, just attack. When the match begins, drive forward. Don't let your opponent breath, don't let them think, just keep attacking until the match is over and you are pulled off your opponent. (desperation)
But don't just try these out once or twice. Try it over a period of two or three months. Or even in combination. (the first and fourth work well together)
After a long enough amount of time, any problems you have built up will work them selves out. Good luck, and you know what, the shy kids are the power behind the king. :asian: