Hi gryffindor9, and welcome to Scarleteen.
The idea that people who are not straight/cisgender "just know" about their orientation/gender identity from a very young age is a common one, for sure, and it does line up with some people's experiences: there are some folks who are certain from very early on what their orientation or identity is, and don't experience much if any shift in that. But sexuality is incredibly diverse, and so there are also plenty of people who don't "just know" early on (including people who end up identifying as heterosexual and cisgender!). It can take a while to figure out who we're attracted to and sometimes, too, that can shift and change over the course of a person's life. It is often confusing, for sure, but if it helps at all, you're so not the only person who's gone through this, far from it.
That feeling of wanting some certainty is also something that a lot of people experience, but unfortunately, figuring out who you're attracted to and how you might identify tends to take some time. Particularly if you've not been strongly attracted to anyone before this, even figuring out what that feels like for you might take a while. When you say that you might like this girl, can you talk about what that means a bit more? (For example, often people find that when they have a crush on someone, they want to spend all their time with that person, want physical contact of some kind, feel tongue-tied or shy around them, etc.)
If you do feel strongly that you want a term for your sexuality, "questioning" is a perfectly valid one, and you might find that works for now while you're still figuring all of this out. We have a piece about questioning if you want more info on that:
Q is for Questioning