Teach him how to "stutter" voluntary, easily, without stress. It's normal for kids, growing up and learning to talk, to hesitate, repeat or prolong words or syllables. Someone, sometime might have attracted your child's attention to his speech pattern, he might be more sensitive than others and react to this. I wish someone would've told me when I was a kid that repeating, prolonging or hesitating is normal. Your child is perfectly normal, don't get caught up in the "researches" that imply there's something different in the brain. We just tend to be "hurried" when doing anything, and as children, we try to talk fast when we haven't developed our speech completely. As for you, start by watching the series in the link below and you'll understand better what I meant. https://youtu.be/EQUBiOdXlig