My family sort of suspected my whole life, but I was officially diagnosed when I was around 17 or 18 officially, after having been previously diagnosed with a sensory processing disorder and some other comorbid conditions. It was good in some ways, because it validated my experiences and now I can better get help and understanding from school, for example, but it also has been used to insult me and call me a "freak", and some people call me a liar about it, because I'm a girl and I do a pretty good "passing as a quirky neurotypical" routine. A lot of people were actually kind of mean about it, so be careful who you disclose it to. I didn't get a lot of accommodations either, but that's mostly my fault because I was diagnosed so late I don't even know what to ask for or how, and I'm terrified of confronting people about it. (So don't be me! Be an advocate for yourself!) But it has been good for me in that I understand myself better, and I can kind of be my own therapist, if you will, because now I know why I struggle so much, and I can find others who get it and get tips about how to get help online or in books, or even by discussing differences in perception with people.
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"The important thing is not to stop questioning." -Albert Einstein