I never stutter when talking to myself.. Rarely with friends.. Always with my family/strangers?!

I never stutter when talking to myself.. Rarely with friends.. Always with my family/strangers?! How does this make sense? When i'm talking to myself or whatever, (thinking etc, you get the jist), i never stutter. Occasionally i have minor bumps with friends. But when talking with family or strangers, i get blocks often. What is particulary weird is that i can sense which word i will block on long before i say it. Any advice?