I know how you feel. In my school years I thought of ending it all, but what would that help? There are things worth living for. For me, it is marrying my fiance one day, having children, having grand children and being a kick ass grandpa haha. I just pray to God my children won't stutter. I don't want them to have it like us. It's hard as a motherfucker!!! Can't you do the presentation private? Like just you and the professor? Maybe after class? That might help. At least you won't have an audience to deal with.