I'm not an expert, but did have such a stutter as a kid, it's mild now as an adult. I'm speaking from my own experience, take it with a grain of salt and do what you think is best. My advice would be; - not to make a big deal out of it. - don't give him advice like "breathe", "speak slower", leave him be. You may be one of the lucky one's, like with my daughter where it may go away on its own. - definitely see a speech therapist. - if his stutter is stressing you out, it will stress him out. Be supportive (but please don't give him advice). I feel your pain. I sincerely hope it's not a long term thing and that he gets a the support he needs. It can get better, you can live with it.