My son who is the same age as you has a diagnosis of autism but this was given after months of tests, reports from all people in his life and only after we were really sure it was that not something similar. Especially in children some things aere easily mistaken for others and it is only apparent when they become 'cured' in later life! At your age he was tempted to get an ADHD diagnosis as well but decided in the end there was more to life than collecting labels. He was lucky however as the initial diagnosis gives him the opportunity to sit his exams in a separate room and a little more time. He never takes up this extra time as the ADHD side of him means it is hard to stary still and concentrate for even the shortest time.
I hope you manage to get things sorted for you. I can understand your wish to get a diagnosis if it could help you in school but remember you are more than a collection of labels.