I have a tip for you. Try to save a photo of a random crowd and open it full screen on your computer or any other device. This is your training ground imagining that you speak in front of a big audience. This is where you should face your fears. All you need to do was to keep practice, know what you wanna talk for every slide that you present, etc.
It’s okay to be a mess in the first place, but as long you keep doing it, you will be getting much more comfortable. Your fears will slowly die down. This is what I do when I am still at the early stages of my speaking engagement. No speaker is perfect, everyone makes mistakes (even the pros).
This is exactly what my professor have told me in my senior year in highschool, what I mean is that all those tips are what my professor said, I don't know but you might be that professor, just kidding. I think that this tip is a proven one and also good luck for your future invites to speak.