It's literally IMPOSSIBLE!?

I can NOT get my homework done AT ALL. NOTHING! I'll get sidetracked with something else going through my mind and forget all about homework. And it's nothing like "Oh I forgot to do this" or "Ooo! I'm gonna go play outside!" It's stupid stuff, like "What would happen if the world turned into burnt toast smothered in erless appleless apple er?" (Yes...I'm dead serious...and I'm not 3. I'm 13!) Then that'll bring me to another thought and soon I'll forget all about what I was doing! This happens in school all the time, too. My parents most likely won't get me checked out for ADD. My dad just tells me to "train myself". I've tried and I can't! I'm dead serious, too. Like when I always said my back hurt before I was diagnosed with scoliosis (scoli means your spine is curved) he'd say "You're a young whipper snapper! You're back shouldn't be hurting!" Please help me! I seriously think I have ADD and no one will listen...what do I do?!