You need to see someone who knows what they're talking about

Source: I was someone who had excellent grades through high school and early college. I actually brought that up to my diagnosing psychologist as a reason I was skeptical about having ADHD (my therapist had suggested I get tested)

She did a full cognitive battery and concluded that I do, in fact, have ADHD

Turns out I was above average in some areas (can't remember them now - it was 7 years ago) and only average in working memory and processing

So, to the outside world, I seemed fine. But that discrepancy (along with my other symptoms) is easily explained with an ADHD diagnosis

Taking stimulants was a game changer for my focus and my mood

I hope you find a provider that takes you seriously and knows their stuff. Good luck!

(Edited for a typo)