Made me (diagnosed with ADHD-I) chuckle, that could definitely be me. Usually one of these:
Forget the appointment altogether.
Remember appointment, be unable to do anything beforehand, find something to distract me of that impending appointment dread, forget the appointment that initially took up my entire attention span.
That's rough, sorry to hear that. I only got diagnosed in my late 30's, ever since high school I felt like something about me was off.
Daydreaming? "Well, you've got an IQ of 135, so you are just bored."
Incapable of starting homework? "Completely normal, you are just bored, try harder."
At some point I convinced myself I was just lazy, it was only when I hit a roadblock professionally I was finally able to convince a doctor that this could not go on any longer.
It sucks knowing something is wrong, but having to fight to get taken seriously. I hope you are able to find the help you need soon.
I opted to do the second one, except i actually went (and arrived early. Military brat upbringing yay, "early is on time, on time is late, late is unforgivable") and then completely failed at coherently expressing the symptoms that make me feel like i have ADHD. Mind went completely blank and i spaced out.
I'm writing notes on my thoughts as i think of them now, its easier to compile my thoughts that way and if its written down i wont have forgotten absolutely everything like it's the day of a test in school.
Once I've got enough notes I'm going to try another appointment and just... hand the psychologist the list of notes.
Yeah, that's how it usually goes when I go to the GP. Can't express myself, mind goes blank or gets tangled in what I want to say. For my 'I think I might have ADHD' talk I also wrote down everything on notes, condensed them to a checklist and just worked through that. Really helped in getting a coherent story across.