I received my dx at a young age, and sometimes I feel like I don't have Autism, or people tell me that I don't "seem Autistic."
It is true that I don't have obvious problems with eye contact, metaphorical thinking, tone of voice and expressions. I used to have more problems with eye contact, I'm told, although I don't remember. I had more issues with conversational topics, situational cues, and more subtle or less overt problems with nonverbal cues (inappropriate smiling or conveying sarcasm or irony). Sensory issues were not as intense since I started high school. I had basically one routine that I enjoyed and would melt down if it was violated, but that was about it. I had many other rituals that were attributed to "Autism", but were really OCD. I also had OCD fixations that were separate from my ASD interests, but doctors conflated them, too. However, I did stim frequently. I have only experienced "shut-down" once, mildly.
Thinking back to high school, I did so much stuff that I didn't realize was socially awkward back then. Therapists in their office would be shocked at my Asperger's diagnosis, but none of my classmates were. It made more sense to my peers who saw me regularly than therapists.
People who see me one on one and older people also frequently do not believe the diagnosis. Socialization is much easier in a stable environment with steady topics of conversation, and I think older adults are more tolerant of differences. Younger people are hypersensitive to others who act "different."
Like, when I look back on it, I feel that the diagnosis was accurate, but many times I don't "feel" Autistic until my next social blunder happens. I think that "Autism" is not really one thing, but a range of symptoms and presentations of symptoms that are incredibly varied. When two of us say "I have Autism", we may be speaking about different underlying factors that have all been grouped under the same label.
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AQ: 36 (last I checked :p)