Stuttering is a very curious thing. Mine has always fluctuated, sometimes by the month and sometimes by the hour. Even the sounds that give me trouble tend to change over time. I've stuttered since I could talk, but I only became self-conscious about it when I hit puberty and got into Grade 8. My whole style of speaking changed then. I also usually stutter worse with my parents than almost anybody else. I'm not sure there's a scientific explanation.