I used to be TERRIBLE at public speaking. My hands and voice would shake, and people in the audience would whisper about it or laugh. Occasionally I would forget what I was going to say. I came off as very unconfident. It was something I dreaded. I'm still nervous about it now, but I learned a lot of great tricks from taking a public speaking class in college actually (I'm a Senior too!).

The most important thing is to practice. If you're nervous, the best thing to do is to endlessly go over your presentation until you have it down backwards and forwards. Talk it out with your cards first, and then without your cards (though during the actual presentation day, use the cards as a back-up). Practice using gestures and modifying the tone of your voice. It really does work because when I'm nervous, I immediately go to autopilot; I'll do whatever comes naturally because I can't think when I'm nervous. And your speech will (usually) come naturally if you practiced it a ton because you're used to doing it. I know that sometimes you might still forget what you wanted to say or not say it perfectly, but this really does help a lot.

Good luck with your class, I hope it goes well. The most important thing is that you get up there and do it, whether you do "well" or not!