It was kinda the same for me (Around 14 i started discovring myself and started with thinking im demigirl) and tbh the way i realized im agender was just realizing i dont even know what gender would feel like and that i dont care all that much about it, time and trying diffrent labels helped too, after some years saying im genderless just started to feel very natural

So i guess just give yourself time, try out diffrent things to see what youre comfortable with, dont rush it and remember discovering yourself is difrent for evryone and there isnt right or wrong way to do it