You may have an anxiety disorder. It is difficult to know which anxiety disorder you may have. The symptoms you have described are characteristic of panic disorder, which is a type of anxiety disorder. If I had the opportunity to interview you in person I may have a better idea of which disorder you may have. Please keep in mind that it is nearly impossible to offer a diagnosis over the Internet based on a short letter. This is why I always advise individuals who are requesting a diagnosis to seek an evaluation from a mental health professional in person. I would highly recommend this for you.
Anxiety disorders are treatable mental health problems. Cognitive behavioral therapy is known to be an effective type of treatment for anxiety disorders. Cognitive behavioral therapy for the treatment of anxiety disorders means that a therapist would try to understand the way you are feeling. He or she would also analyze your thoughts, help you understand that many of your fears may be irrational, and try to replace those thoughts and feelings with more rational ways of thinking. The behavioral aspect of cognitive behavior therapy would be to teach you new ways to behave in situations that make you nervous. Cognitive behavioral treatment may also include teaching you effective stress management techniques, training you how to prevent nervousness, and so forth. Some people also find that medication is helpful with anxiety disorders. The first level of treatment at this point, ideally, would be individual therapy.
Based on your letter, it seems that your symptoms are consistent with an anxiety disorder. I am not sure if it is a full-blown anxiety disorder. Nor can I determine which specific type of anxiety disorder you may have. What is evident is that you could benefit from treatment. If you have not done so please speak to your parents. They may be able to help you with your anxiety. They care about you and may have helpful advice. They need to know that you are experiencing a high degree of anxiety so they could either teach you how to deal with those symptoms or attempt to find you professional help. Thank you for your question.