I broadly agree. But it's difficult to talk about this subject because of the ambiguities of the lexicon involved. If we're to ask whether we "existed before," it's important to know what, exactly, we mean by that. In other words, we need a clear framework for talking about the nature of the self. Without that framework, our discussions are necessarily clumsy and vague.
I will nevertheless to talk a little bit about what I believe. I believe that there's no meaningful distinction between "me" and "you", when we really get down to it. Sure, it's useful to talk about me being me and you being you, since the world functions more cohesively like that, but there's no physical point at which my consciousness ends and yours begins. There is simply, in each moment, consciousness, existing in different ways, emerging from different places, but ultimately not "in" any physical place. We talk about ourselves experiencing things, but consciousness isn't experienced "by" anyone or anything - it's something that simply is, existing as a consequence of physical states of matter. We talk of our minds as if they were a facet of ourselves, something we exert an ownership over, but we are our minds, which are caused by physical matter, and that physical matter controls us totally - it would be more accurate to say that it owns us.
We talk imprecisely about our own personhood, most of us living under the impression that we are the same person as ten years ago, and will be the same person in ten years' time - we will have changed in some respects, but our identity will remain the same. In reality, we don't have any reason to think that's the case. If we built an exact replica of ourselves, we would be two distinct people who merely looked the same and behaved similarly. The same is happening to our bodies, being slowly overwritten over time, being subsumed and taken over by a new identity.
Everyone goes through life so caught up in the notion of the self, but it's likely an illusion. I am as much me as I am you. Two consciousnesses, existing in space-time, disconnected, but not with meaningfully distinct selves.