I have three answers.

a) I don't care where I came from. I don't think free will exists. (As in, I don't think so, but I'm not 100% sure.) Why then would I be concerned with something I had no control over? Knowing where I was also won't help me affect where I'm going in that case.

b) Assuming I'm wrong about free will, then I believe that one should be able to apply themselves, and through effort achieve what they want in life. Now that said, I'm not going to be able to be an astronaut at this point in life, no matter the effort I put into the cause. So only to some extent am I concerned with where I came from. Basically, I've gone too far down the wrong path to be an astronaut, but I can use where I was to determine where I'm going, or which direction I need to go to get where I want to be. However, I'm still not concerned with where I was before I was born.

Basically, a and b are dealing with consciousness, with my existence as I current understand and define it. Which brings me to c.

c) The particles which make up the atoms that make up my body have existed since not long after the Big Bang. (The smallest of) Particles weren't created in the Big Bang. They were already there. Space and time were just compressed down to the point where space and time didn't exist. The Big Bang wasn't an event that created things. Everything just expanded. That expansion is what created space. And the creation of space also brought time. The fact that there could now be two events or objects separated by space also meant that there would be an amount of time required to to get from one event to the other.

I said that to say this: I already know where I was before I was born through physics.

Take all the atoms that make up my body and ask where they came from. The Earth, obviously. I surely wasn't born on Pluto. But where did those atoms come from? Go back further than that. Stars fused hydrogen into heavier elements. Those stars shed off their outer layers when their cores collapsed, and sent the elements they'd created out into the universe. This probably happened over and over for a very long time, with heavier stars creating heavier elements. That's how all the atoms that make up my body came to be; I'm star dust. We all are.

But what about before that, before we were all hydrogen atoms in a cloud that would eventually condense to form a star? I don't know what caused the initial expansion we call the Big Bang. If I did, I'd be famous. But it happened. In that early expansion there was a crazy hot soup of subatomic particles and antiparticles banging into each other, going into and out of existence. Somehow, matter slightly won out over antimatter as things further expanded. As things further expanded (we're only taking about 10^-6 seconds here), it cooled off enough for these subatomic particles to start forming protons and neutrons as they slammed into each other and our current model of physics came to be. About one second in we had electrons and positrons. Within a few minutes, or further expanded and cooled enough so some of the protons and neutrons were able to combine to form what would be the nuclei of atoms like helium. Most wouldn't combine.

At this point, just a few minutes after the initial expansion, all the parts needed to form atoms existed. However, it would another 375,000 years until the universe expanded enough to cool to a point allowing the electrons to convince with the nuclei (mostly just protons) forming hydrogen.

Many scientists believe that the existence of dark matter up to this point was what caused there to be pockets of enough gravity to start pulling areas of this hydrogen together, which would eventually form the stars, and thus everything else.

So this is where we all came from. This is where we were before we were born. You don't need to go back further than the Big Bang. Time did not exist for the singularity. You can't ask, "where was I?" before "before" even existed.

Now, if you've followed me this far, here's my final point. Metaphysics doesn't matter. It's not going to tell you anything significant. Asking where your consciousness or being was before you were born is sophistry and paralogism. Your consciousness is your brain. Your brain is made of atoms, and physics can tell you where those atoms were. Not theology, not metaphysics or any other firm of philosophy.