DS is 6 and a half and for the last year has been chewing his collars and cuffs. He is putting holes in all his clothes and within a short time of putting a top on it's soaked through. He does it in all sorts of situations but mostly when trying to concentrate or if he's in a new situation so possibly linked to being a bit anxious. He'll also do it while watching TV so it's not just that. It's particularly bad at school as he does it like some people might chew a pencil. I've tried him with one of those chewy necklaces but he says he only likes the feeling of cloth so that didn't help.
Is there anything I can do to stop it? I can't afford to keep replacing clothes that's he chewed through and the constant wet clothes next to his skin is giving him rashes, plus I can't imagine it's good for his teeth. Help!