I didn't know as a child. I had no idea. It wasn't until I was like 28 or something that I realized I was trans. Before that, I never would have said I was suffering or struggling with my gender or anything. There wasn't any gender-related pain I could point to. Then suddenly one day hearing myself referred to as "she" just rankled for some reason. It didn't feel right and this feeling of wrongness came out of nowhere, very strongly.

But a weird thing happened after I came out to myself and a few people around me. I started recontextualizing some childhood experiences and feelings and I realized, holy shit, I've always been trans, there was gender dissonance, I just didn't recognize it for what it was.

In time you might feel some of that, I suspect many trans people do. But even if you don't, that's ok! I'm not a person who thinks gender (or sexuality) is always innate and unchangeable. I think humans are malleable and our genders and sexualities can change, just as other aspects of our identities do.

Let yourself consider that you might be trans! You definitely don't need to have felt dysphoria for years, just not wanting to be a cis man is enough!