TeenHelp - awful, awful anxiety.

I think the first thing is to identify what has led to you having bad anxiety. Is it because you are having to give the presentations or did the presentations make it worse? I think if you can work on identifying the triggers that can help with longer term solutions to the anxiety. It might help to keep a notebook and write down when you start feeling anxious and then write down what happened. You can also find anxiety or mood apps for your phone that might help you with that.

There are short term solutions to anxiety but a lot of those times what works for one person might not work for you. I'll list some of the things that have helped me and maybe they will end up helping you.

When I have presentations or things in school/work/stores that cause me anxiety I will bring something to fiddle with. Sometimes it is a worry stone, my phone or a soft item like putty that I can play with.
When I used to have to give presentations for school I would make eye contact with the teacher and no one else. It might seem weird but the teacher was safer than the rest of my classmates
Hot showers help me too. I don't make the water too warm but the heat and steam and the water help me to calm down
Reading helps me to stop overthinking and worrying because I have to focus a bit more on the words so that the story makes sense.
Cuddling with my animals
Talking to my boyfriend
Journaling or logging my moods

Something you could do is look up the Alternatives and Coping Methods some of the things listed might be good ways to cope with your anxiety. It will probably be trial and error but it can sometimes be fun to try the different things.

I hope this helped. :)