I don't think it's happening because of the exercises. Probably you started paying more attention to the stuttering itself because of the exercise? Or you expect results because of the exercises and that way you focus more on your speech (and you try more to speak perfect) ? I tried just abdominal breathing and tried to make it as a habit everytime during the day and it worked for me very efficently. What else works for me is : trying to be more spntaneous... I realized that people who do not stutter doesn't care and don't prepare that much before they talk - they just talk, they even don't know how long they would talk they just let the flow. I was reading a book a while ago and the author impresed me by saying: "I don't even know what I will tell .. How can I know what I will say and what I think if I don't speak about it first?" (the book was about making more friends)