Sort of a complicated question, I'll try to ask. How was I born me and not another?

[Arkilogue]

I've come to conclude that this is actually an absurd question.  You're you because if you were me, you would be me.  You may as well ask why one tennis ball isn't this other tennis ball.  Because one is made up of a certain set of atoms and the other is made of another.  You are a certain set of neurons inside a certain skull that has evolved to create a self-identity based on things like brain structure and experience.  

You're not a rock, because if you were a rock, you couldn't ask this question.

The key here is the trajectory of "me" based on the accumulation of experiences both objective and subjective, conscious and unconscious.

If you had different experiences or made different choices, you would be experiencing a different self identity.