The same thing happens with me, the exact thing about pity and don’t want other person to wait and all .I think this is what goes on with many stutterers. I don’t think you can control it. I think what you can do is start facing the same situations like talking to someone new everyday or something like that. I never used that :P but I think this would help you and me. I have couple of exercises which helped me ( pm me if you want to know those I can tell you what worked for me )but I was scared to use those techniques in my second language , I was just scared to fail cause my first language was almost fluent so I didn’t work on that and now I regret it ( what if you know )and then I stopped doing my exercises . Rest I think some professional might be able to help you better hopefully.