What has helped me the most is to disclose my stutter to my instructor, then at least they know, and it hopefully won't effect your grade. The best advice I have is to not think about what you say before you say it. If I plan what I'm going to say, I always get stuck. Also what helps me the most is remembering that my stutter bothers me much more than it bothers anyone else. Most people just wait patiently and it can be awkward, but they'll forget about it or move on pretty quickly. If people are rude they're the assholes. Good luck in your class, sorry stuttering is causing you so much stress