The most common reason for a smelly dog is blocked anal glands. Dog groomers are used to clearing them as are vets. Although it's a very simple squeeze technique, it's not the most pleasant thing to do so I'd get a professional to do the dirty work for you. He'd need a bath afterwards then should be much more fragrant. If that fails have you checked out his teeth?
thank you all i know his teeth are fine the groomer said its his anal glands also because he drags his butt on the floor and i now he doesnt have worms so he will be going to the groomer to have his glands cleaned