Can someone explain this to me?

Can someone explain this to me? I am a lifelong stutterer, my stutter was horrible since I learned to talk up until 4th grade. Then it suddenly almost "stopped." I occasionally had a couple blocks every now and then; but it was nowhere near as bad as it was. Then I got into junior high and it "came back" as in the severity of it increased substantially, mainly around my parents. I am now a junior in high school and I still have my stutter. However, my stutter is very severe around my parents and family, but it is light to mild around my friends at school. So my question is: Why would my stutter seem to "stop" when it did? And why is my stutter more severe around my parents rather than my friends?