Personally I would encourage the phrase, "I think I have autism" or "I'm self-diagnosed" just for transparency's sake. You will receive support here regardless of your diagnostic status, but others' knowing whether or not you have the label on paper will allow them to help you better, since they'll know to tailor their advice to the sorts of things you'd have access to as an undiagnosed person, rather than services you're presently unqualified to receive.
I also recommend self-diagnosis as a stepping stone to professional diagnosis whenever possible, since I personally don't see the point of claiming a label which does nothing for you unless it's written on paper. Just my two cents.
_________________
"Survival is insufficient" - Seven of Nine
Diagnosed with ASD level 1 on the 10th of April, 2014
Rediagnosed with ASD level 2 on the 4th of May, 2019
Thanks to Olympiadis for my fantastic avatar!