I have ADHD and wasn't diagnosed until later in life. I wish I had been diagnosed when I was much younger.

I would not give up seeking help for this. It is crucial that you get an adult to listen to you. I would as the poster before me said, to go to your school counselor. You may even talk to your school nurse if you have to. We know ourselves better than anyone else and I believe you when you say that you want to succeed. Please keep reaching out at home and here. Welcome to PC.