I only got diagnosed after happening to see a psychiatrist who (it turned out) specialised in Autistic Spectrum disorder. It wasn't something that I thought of prior to that. To start with, I didn't believe him.

But he asked a bunch of questions and stuff started clicking into place. Things I never thought of before. How I was slow to learn to feed myself. How my Mother used to lay out my clothes and I'd have a screaming fit about that most days. How I used to collect toy horses and spend hours lining them up and learning random facts about horses. Even my interest in English Literature, later. Apparently that is quite common for girls, too... I didn't think any of this was relevant to my mental health. Nobody had ever asked me about that stuff before...

And how they let me into the DBT program but said I didn't really seem borderline... But might find learning the skills useful for coping. I didn't have the whole fear of being alone thing... But my sensitivity to environmental stimuli surely did trigger sensory overwhelm / meltdowns / something perhaps akin to borderline upsets...

Anyway... I certainly remember that feeling of knowing which part of the diagnostic stuff the clinician is feeling comfortable ranging over (ooh there are the psychosis questions... Checking out the mood... Checking about the manic thing again, I think this doc really wants me to be manic...)

(when all you have is a hammer - everything looks like a nail).

Is there any way you can get referred to someone who specialises in Autistic Spectrum? Maybe try contacting a consumer group. I had trouble finding a GP / clinic where the nurses weren't trying to grope me to weigh and measure me all the time etc etc and the local group here gave me the name of a GP and clinic who turned out to be really terrific. Luck.