Unfortunately the stuff that worked for me (Adderall) is basically just meth, and I can't get a hold of it in Japan on account of it being illegal. I think it's not even very possible to get a hold of ADD-related meds outside of the US (France classifies it as a children's disorder, so after 18 tough luck).
Different molecules, different delivery systems, different dosages, different therapeutic goals (euphoria not being one of them).
I would agree that "basically just meth" may not be the best way to say describe this, though, as it's only as true as saying they're entirely unlike meth.
I definitely agree that you should see a specialist. Please don't be reluctant about it.
The tests that are done to determine whether someone has these disorders are non-trivial and are accurate.
At your age, you decide what kind of treatment is best. You can definitely start with diet and move on to medication.
The best thing in the world I ever did was go see a psychiatrist to get tested to see if I was ADD. After the test came back positive, he prescribed meds, and after finding one that worked for me, I was simply blown away.
I never knew that you could actually think about one thing at a time before. I never really understood what it was to have a conversation and not be thinking about a billion things. I never, ever, knew what it meant to focus on something. It's entirely changed my world.
Wish you well my friend. At least go get tested. If you decide to take meds or follow some other avenue, it's better to know what you're working with.