OP, I know what you're talking about and unless you've seen it people can't know how scary and disturbing it is. DS is being treated for anxiety. One of many things he did to hurt himself over the last year. He pulled out 4 molars during the last month of school last year and his two eye teeth during the first week of school this year. These teeth had no play in them at all. they would make crack and popping sounds when he would yank them out and blood would gush. The other children around him at school were scared by it. It wasn't normal wiggling and pulling.
Is he hurting himself in other ways? Pulling at the skin around his nails? tearing his nails? (DS nearly pulled one nail out) Hitting himself? Calling himself names?
It may be nothing, but if it's worrying you or if there are other symptoms, talk to your pediatrician.
Oh, and no your son isn't disturbed. He may be having anxiety problems or there may be something bothering him (or as others have said he may just hate the feeling of loose teeth), but I think disturbed is too strong a statement.