Thank you for writing. I don’t know if you have D.I.D. I do know that you need to see someone who can help.
Your grandparents are correct that nervousness is part of life at times, but what you are describing isn’t the same as garden variety teen nervousness.
Please listen to my voice instead of the voices in your head. Do talk to your grandparents about getting some therapy for you. Reassure them that you aren’t looking for years and years of talking to someone — which is a common misperception of therapy and may be their worry. Instead, tell them that you are so upset so often that you just want an evaluation to help you understand what is going on. If there is a diagnosis like D.I.D., the therapist will help you explain what you need to your grandparents.
Please follow through. This problem isn’t likely to go away by itself.
I wish you well,