The most fundamental question of ontology is not exactly "why do I exist" but rather "why does anything exists rather than nothing?"

You don't know a lot in philosophy. The only consensus is that you know that you exist, which implies that at least one thing exists rather than nothing.

But nothingness would've been a lot simpler right? When something exists then there's the question of what. Who chose the content of what exists? My faith tells me no one since I'm also atheist.

Now you might be tempted by simply saying that existence is just chaotic and random and all the rules of matter just spontaneously spawned out of the void for no reason but think about it : the possibility of randomness, the possibility of time and space themselves, that's a something. If there are dice in the universe that generate random realities then those dice are not nothingness.

So basically what I'm personally convinced of is that, in a good little materialistic fashion, all is driven by necessity. We exist because it was necessary, so you're necessary. Things are how they are because they generate the most something

My final personal conclusion to the existential crisis is that something has to observe the world. The rules of matter had to end up with life eventually because life it is the most something of all things. Intelligent life is the only thing we know of that can observe still matter, the universe without life doesn't really exist because nothing is here to observe it.

So there it is, your freshly delivered atheist purpose of life : create a something that start existing, and contemplate all the things that exists. You are a vessel of the bare concept of existence, you're the product of the necessity of existence, you spawned to create and contemplate because something had to exist