I would focus on how to better communicate to your wife what’s happening (you’re having a hard time getting the words out, but you aren’t mad) than trying to change how you speak. I mean, if you can, great, but if you can’t, she should be able to understand that you are speaking the way you do because you stutter and not because you are angry. My husband stutters, and it was hard at first to know, at times when he was being really quiet, if he wasn’t talking because he was upset about something, or upset with me, or had just had a long day and was tired and didn’t feel like talking. Now I know that it’s almost always the last one, but it did take some time for him to realize that he did need to somehow let me know that things were okay with him and with us even though he wasn’t talking. Even a non-verbal signal like smiling and squeezing her hand so she knows you aren’t mad at her could help.