My advice would be to not only rehearse your speech, but also get into the mindset of not giving a shit, right now you're overthinking it and that's natural, but the more you ruminate on it the more you build it up in your head as this massive, impossible thing you can't get done. Fundamentally, most of not all the people in the class won't be anyone significant in your life in the next couple of years, so their opinion of you has the same value as what you leave in a toilet bowl. It may not seem this way, but most people won't treat you poorly because of it, the anxiety can make it seem like more people will get on you. Sadly it's the vocal minority of miserable pricks that like to shit on others to uplift themselves. As for tips, if it's like my English classes used to be, each person gets their turn to speak, going first can be a bit daunting. Ask your teacher if you can be one of the first so there isn't a build up to yours. A trick I used to use is I'd pretend to myself I was going to say another word than what was actually in front of me, then at the last second I'd say the actual word that was written, it worked for me more than it didn't. All the best to you.