It sounds as if you are fed up with your anxiety. I find this encouraging because it may signal that you are on the verge of making a positive change in your life (i.e. getting rid of your anxiety.)
Anxiety is a very common problem. People develop anxiety for multiple reasons. In your case it seems as though it may stem from a lack of self-confidence. You are focused on what other people think of you. Apparently, in your mind, you have established that you are not “good enough” and thus feel anxious.
You are frightened of public speaking. You are not alone. Most people share this fear. Surveys have shown that the fear of public speaking often ranks higher than the fear of death. This means that people are more frightened about the idea of speaking in front of others than they are of their own mortality.
When it comes to public speaking assignments, a common mistake in the thinking students make is that they believe they have to be an “expert” on their assigned topic. The reality is that you are a student who has been assigned (i.e. forced) to give a speech to the class. No one in the classroom, including the teacher and especially the other students, expects you to be an “expert” on your topic. Students are not expected to be experts. You may be putting undue pressure on yourself to be something that you are not (i.e. an expert). Try to have a more realistic mindset. Study the material, learn your speech, share what you have learned about your topic with the class and simply try to be yourself. Do not try to be an “expert.” Don’t try to be something you are not because it will only increase your nervousness. Just try to be yourself and this should decrease your nervousness.
The key to eradicating anxiety is to believe in reality. Anxiety is based on unrealistic fears. Believing in the unrealistic fears is what keeps the anxiety alive. Anxiety thrives on irrationality and illogical thinking. You may believe for instance that you do not make a good impression in front of others and this increases your anxiety. Just because you feel as though something is true does not mean that it is. You may feel as though you do not make a good impression in front of others but what objective evidence do you have to support this assertion? It is important to analyze the facts in every situation. Search for objective evidence and let reality guide your feelings.
If this continues to be an issue, I would recommend seeing a therapist. That would be the most efficient and effective way to deal with your anxiety. You can also speak to the school guidance counselor. Inquire whether he or she has any tips to share with you about how to improve your self-confidence and decrease your anxiety. You may also try reading self-help books. I would recommend The Anxiety Workbook for Teens: Activities to Help You Deal With Worry and Anxiety by Lisa M. Schab. I wish you well. Please take care.