It is very difficult for girls to receive a diagnosis or to be recognized as autistic.
You need to get a diagnosis, especially since you speculate that you might be autistic... I did not think I was autistic until I found a psychologist who I believe to specialize in sexual trauma; however, she also specialized in autism and I spent our entire first session talking about Sylvia and that is when she asked me if I was on the spectrum and that led to my eventual diagnosis; however, I was almost twenty one at this time! I had just always thought that I was a psychotic, yet passionate introvert who had trouble relating to the rest of the world...
Often when I would have meltdowns in high school at school-- though most of my meltdowns were in the morning, almost every morning-- I would often run away, hide in the bathroom or hide in my favorite teachers room or skip class and hide under the tables in the cafeteria and after an initial trauma, I was allowed to go to the counselor's office. Have you tried going to the school counselor or maybe when you feel the rumbling phase, you can excuse yourself from the classroom and find somewhere to hide...
And yes, I would say that not having a diagnosis does put you at risk for ill treatment; be careful around police until you get your diagnosis... I am not going to tell you my experience with the police so you will not freak out; however, just try to get a diagnosis. Also, if you need to talk about anything, Private Message me... I too was an undiagnosed seventeen year old girl, so I understand...
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"All by myself I am a huge camellia
glowing and coming and going, flush on flush."
-Sylvia Plath, Fever 103