I'd recommend everyone who thinks he or she has ADHD to keep in mind that there are clinics who literally make money by diagnosing you. So make sure you don't go to one of those. This is a problem, even in the Netherlands
https://www.trouw.nl/zorg/in-de-adhd-fabriek-is-de-diagnose-... I wish I could find a translated version for you.
Anyways, Methlyphinidate (ritalin) should be your very LAST step. Before that, clean up your workspace, disable distracting apps on your phone and computer, use a site blocker... And consider that a lack of discipline is not caused by ADHD.
I speak with experience here, because I was "diagnosed" with this "mental illness" before it was cool, about two decades ago, when the teachers noted I couldn't pay attention in class. Took ritalin for about a decade. Always thought I had trouble concentrating, like I was told right? Well, a few years ago I rented an office space with a friend of mine, just the two of us in a very spacious (100m2), light and well-ventilated office. We received no phone calls, there were no people walking in, or cats and girlfriends asking for attention. I had less distractions than I had at home, and much less than in a traditional office. And it was a dedicated area for "work". A comfortable desk and chair, two monitors and a fast pc.
Having worked in such a proper environment, I will never say I have trouble concentrating again.
Anyways, what exactly do you think you have to gain by being "diagnosed" with ADHD?