I don’t tend to notice this effect in my life. I’m really so sorry if it’s affecting your life negatively in a way you don’t want mate. I honestly lack advice in terms to stuttering here, since this is solely in your mind. It may be intrusive thoughts in this case since your mind is talking and you don’t want to to talk that way, some form of distress in thoughts. I’m not aware of anyway to directly fix it though, sorry man. All I can say is, accepting your situation and being true to yourself is one of the better remedies for dealing with intrusive thoughts and the mind’s chatter.