Laziness or ADHD?

Hi I'm 15 turning 16 this year. I'm reaching out hoping to get an answer to a question I have been wondering since 7 or 8. As a child I've always had a suspicion that I could have ADHD I had brought up the topic to my parents on multiple occasions throughout the years but have been brushed off. Since entering high school my conditions have been getting worse and when I went to consult my parents again I was laughed off and told that I was just procrastinating and that I lacked sleep. They wouldn't even consider sending me in for a simple diagnosis and won't budge on their stance. I'm hoping I could get a diagnosis before graduation as I don't want it to affect my studies whether I have it or not. I am posting to get a diagnosis or more of a assurance that I may have this condition so I can ask my parents again. I have recently took the Vanderbilt ADHD test and it came back with a "presence of ADHD innatentive type" and "presence of oppositional defiant disorder".

These are some of the things I experience:

I have a severe difficulty starting tasks which my family puts up to procrastination, I feel as though I have to chackle myself to my desk to even start work. When I'm putting off doing my work I know that I have to and that I would feel better if I did but I just can't seem to even when I bring myself to my chair. Getting easily distracted, and feeling mentally drained when trying to focus I quite common as well. This has led to last-minute work and sometimes even late work submitted. There are times where it seems like I blink in and out of a situation or that things go in one ear and immediately come out the other. As for the prioritization of tasks, I don't really struggle with this as I understand what is and isn't more important and which is more urgent.

Thank you for reading this through and am sorry I couldn't shorten this without leaving out anything. I hope to hear from the community soon. Questions to help with the diagnosis is encouraged. Private messages are welcome too.

Do I really have ADHD or am I just lazy and procrastinate too much?