As it was explained to me by my therapist during my eval, ADHD diagnosis is generally a diagnosis of exclusion because of the huge overlap in symptoms with depression and anxiety. They basically have to rule out both of those and assume it's ADHD.
Depression:
-Unable to focus
-lack of motivation
-executive dysfunction
Anxiety symptoms (sometimes a result living with ADHD):
-Excessive worry over things needing to be right
-Sensory input overload
-Difficulty sleeping
-Lots of fidgety behavior
So my advice, in this singular case, is lie to the doctor. Don't give any impression that there might be potential depression or anxiety issues. Mine was cool in that they also have ADHD so they understand that it can cause some of those symptoms. But it's real easy when talking to a doc about it to just answer their questions directly and they fill in the gaps with emotional reasons. Especially for women getting diagnosed (There's still sooo much bias for women getting diagnosed and doctors will subconsciously assign more emotion to things). "Does this worry you?" "Does this make you anxious when it happens?" The answer should be "no." You feel frustrated because you know it's something you can do, but those small mistakes still happen." Be honest about the symptoms, but don't admit to being actively depressed. You may know it's caused by life stuff and not brain stuff and the ADHD symptoms are always there, even when the depression isn't, but that's tough to communicate.
So when talking about the symptoms, admit to them, but add where you think they're coming from.
-Trouble sleeping? - Because I'm finally sitting still, my brain is constantly planning what I need to do. Don't associate negative feeling with it. You're not worried about what you need to do, you're thinking about and planning what and how you need to accomplish them and you can't turn that off.
-Unable to focus? - NOT "my brain drifts off and I'm not sure what they were saying" DO say "The person will say a thing that reminds me of something I forgot earlier and while they kept talking my brain continued the train of thought from when I was thinking about that thing before."
-Excessive worry over things needing to be right? - That's a tough one since it's got "worry" right in there, but you want to avoid talking about actual negative feelings. So you say that when you do a thing, often you'll make small little mistakes that you would know are mistakes, but you just don't catch it in the moment (actually another ADHD symptom), so you spend extra time making sure you get it right to avoid that happening.
That sort of thing. Also, if you're going to a doctor first, maybe cut them out. Find a therapist or psychiatrist in the area that specializes in ADHD. You can just go right to them. They may have to send their diagnosis to a doctor, so if you don't trust the ones that have failed so far, you can ask for a recommendation. They know the ones that don't question their diagnosis unless the patient is clearly drug-seeking.