My 3.7 yr old son has been trained for the last year and recently he has been wetting his pants regularly. He seems to do it when he is busy and can't be bothered to go to the toilet. I know he will not do this forever but I am sick of the washing. I have tried rewards and punishments but nothing seems to work. He is far better when he is with me but when he is at nursery he does fairly badly. Any help?