I think it’s true that our attitude as well as focusing on stuttering can influence our tone and intonation, etc. to not be as playful and lighthearted. You just have to relax and not be as hard on yourself. Maybe even tell people that you hope the meaning of what you say isn’t interpreted differently while you stutter. Maybe even ask them if they can teach you to be more lighthearted because you feel like you are serious too often. Make a joke about it👍