How do you overcome the fear of being found out that you stutter?

How do you overcome the fear of being found out that you stutter? I'm 17 and haven't had any friends for 6 years. I sit alone during breaks and try to avoid any conversation. I just feel humiliated when I stutter. I get so bored in class and I wish I didn't stutter because I always want to participate and express my opinion. I don't know what to do because the situation can't stay like this but I also can't afford to embarrass myself in front of the whole class. How come other people who stutter aren't ashamed to speak?