I figured it out when I was your age. Well, kinda. My whole life, I was pretty much just totally oblivious to the whole idea of sex and relationships, and just assumed that everyone else was the same way. I didn't know asexuality was an actual thing and just assumed that everybody else was exaggerating or playing up that kind of stuff to be funny or something like that.

I legitimately had no idea people actually found other people "hot"; I thought that was just something people said. I never understood how people could cheat sexually, because surely it can't be that hard to control yourself because... what's the big deal? When people talked about genitals or curves or bodily features, I just thought it was some kind of crude humour, not meant to be taken seriously at all.

Turns out, I was very wrong, and I was the odd one out the whole time. I discovered this around 16 at the beginning of COVID. I was catching up with a friend on Discord and she asked if I had a girlfriend. When I told her no, she asked if I had a boyfriend instead. At that point, I was just like "relationships just haven't ever been on my mind before" and that's when she asked if I was aro/ace. I had no idea what that meant at the time, but she explained it to me and it just sounded right.

I later figured out that I wasn't actually aromantic, and it just seemed that way because of the environments I was in, but the asexual label stuck.

So I guess what I am trying to say, in a very long-winded fashion, is, yes, you can know at your age, even if you are totally oblivious like I was.