Official autism diagnoses tend to be unattainable for a vast majority of people, so the community in general does accept self diagnosis. The only time I would really recommend that you seek professional opinion on it is if you also have a history of early childhood trauma as that can mimic symptoms and you really need a developmental psychologist with a lot of experience to detangle which issue is causing what problems. That's the reason I went to see who I did, as she has a lot of experience diagnosing people with complex PTSD and autism.
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@Snafu in the Void said, where I live the main reason for seeking confirmation of a diagnosis is to get the government funding you're eligible for which makes life a hell of a lot easier. I didn't initially seek out a diagnosis for that reason (when I made my appointment I was just curious, and it was before I got severe autistic burnout so I likely would have been assessed as level 1 and not qualified for any funding anyway) but by the time my assessment came along I was barely functional anymore.
The place I went to sent out a bunch of forms for me to do, including around 10 pages of paperwork for my friends and family to fill out about my behaviour and traits, a self reported questionnaire that I scored really high on, and I wrote some questions out for my parents to answer as well as a list of things I could recall throughout my life which I suspected were due to being on the spectrum. They tend to like more information rather than less. Then I had a 3 hour assessment where I was asked a whole bunch of questions and at the end got a letter then 6 weeks later a full report.
You could probably get a provisional diagnosis from a clinical psychologist if the full assessment is out of reach for you, which is just as valid but doesn't open many doors to support.
In any case, generally autistic people view self diagnosis as valid because most of us all self diagnosed before getting confirmation and we were just lucky enough to be able to afford it.