my parents won’t let me get tested for adhd

i think i have adhd. for as long as i can remember i’ve had a lot of trouble focusing on tasks and paying attention to the point where it is greatly affecting not only my grades but my entire life. i’m basically failing out of school and it’s not because i don’t care, i just have so much trouble focusing on doing homework that i can’t get it done. sometimes even starting assignments seems impossible and this can’t go on any longer. ever since 4th grade i’ve been told that “i would be better in school if i only tried” but i don’t think people understand how hard it is for me to try, i don’t understand why i’m like this but all i know is that i need help. i told my mom and she said “everyone gets distracted sometimes, it’s normal” i tried telling her it’s more than that but she told me i was being overdramatic. i asked if i could at least get tested just in case but she claims it’s too much of a hassle to find a place to get tested when i probably don’t even have it. i asked my guidance counselor about it and she didn’t believe me either. i’m just labeled as the “problem kid” but no one ever cares enough to ask why i have these problems. i’ve literally been having mental breakdowns every night because i’m so disappointed in myself for not being able to accomplish these basic things on my own and i need help so badly but i feel like i’m so alone in this and that no one believes me. what i do i do? someone please answer, i’m going to college in 2 years and i’m desperate.