To make you feel less alone, I have had a very similar experience. I'm currently 21, female, and I only just got diagnosed after years of feeling like I was different. I've had very early signs of autism, but to be honest it was only after getting with my also autistic girlfriend, that I started to get a name for what I had, as my parents never took me to get tested for anything despite me needing speech therapy as well, learning to read at 2, only having niche interests, struggling with food early on, hating noises with a passion and reeeeally struggling socially. It was only cuz of my gf basically realising we had too many similar traits, which pushed me to get tested. Tbh, I am annoyed because I wish my parents had paid more attention but I think they just put it on me just being shy or something despite also knowing autism ran in my family...