nickkaylee: I don't think many people use the word "retarded" anymore. Not offended, just tired of hearing it.
But to move on, my brother did the same thing as your son. He chewed on shirts (complete holes), his fingers (until they bled), pencils, anything. He also made sudden loud screeches. He grew out of the screeches and sudden movements, but he still chews holes in his cloths and fingers (he's 20).
Worm: Small tics and movements can be a part of ADHD, (I'm going to repeat myself here
) but if he didn't have those before meds, or they are increasing (with or without meds), take him off or be VERY careful choosing medications. I always had small tics but they multiplied after a year of medications (been off for a while, but tics still strong).