Thanks Rebecca for excellent comments - I fully agree with them and would like to add a couple of ideas here.
While your are waiting for your appointments there are a few simple strategies you can use to make things easier for yourself.
1. Learn how to relax your mind and body. there is lots of info about relaxation on the web and also many CD's and apps that can be helpful.
2. Take a deep breath in and out before speaking. this will clear your mind.
3. Prepare a few sentences that can buy you time and that you can use when you get stuck. E.g., "Let me gather my thoughts so i can explain it to you properly", "just a minute, let me think about it".
Dr. Tali Shenfield, CPsych
I don't blame you for being worried about this, it sounds like a real problem. There's several things that could be going on. One possibility is that you have developed an anxiety related stutter or temporary tic. It could also be that anxiety is making it hard to concentrate and express your thoughts. Being 14 is quite stressful--its a time of big transitions and adjustments, so many people your age find themselves having more stress than they used to when they were younger. Stress can make it hard to concentrate. Sometimes as part of anxiety, people find themselves needing to say particular words or repeat words.
I recommend that the first step be to ask your mother or father to take you to your doctor for an appointment. You may want to write your parents a letter like you did here, and help them understand what things are bothering you. The first step is always to go see the doctor in case there is anything medical going on. If you are uncomfortable talking to the same doctor who used to see you when you were in diapers, your pediatrician might be able to recommend a doctor who specializes in teenagers. Its important for your doctor to take the time to listen to what you have to say and take you seriously. Before the appointment, you can ask your mother to request an extra 10 minutes of time for you to speak with the doctor after your physical. You might try writing down what you want to say before you go in, or tell it to your mother and have her help you explain.
Once the doctor examines you, the next step might be to visit a psychologist. Psychologists are good at figuring out how anxiety is interfering with doing what needs to get done. Psychologists can also help you get control over stress. Psychologists are also trained to figure out why your grades might be dropping. The psychologist may recommend testing or therapy. If it turns out to be a stutter, a speech pathologist can teach you techniques so that you can overcome it.
Don't be afraid to tell the adults you trust. Odds are that your problem can be solved, but its very important not to keep it to yourself!
Hope things get better soon!
Disclaimer: This post was written for educational purposes only. It is never intended to replace face to face medical or psychological care.