The only thing I'm sure you're born with is your sex (basically determined by your penis or vagina).
For sexuality, it's just something that you feel, you know? It's not a choice per se, but it just comes to you, and it's also affected by the people, the environment you live in, etc..
(Also I apologize in advance if I'm not allowed to give my opinion on this since I'm most likely straight. I'm not sure if it's rude or not, but a lot have been saying it is.
Sharing too that I'm also at the stage of discovering myself since I used to think I was bisexual but I realized my attraction to women was not as intimate as my attraction to men. But idk, that might change.)