Nobody alive knows, since there is no way to communicate with the dead. A theory I came up with when I was like seven or so was you're actually a god or ghost of sorts living the lives of every living being in your universe, as long as it's observable, and when the one you're spectating dies, you just move on to the next body without noticing. looking back on this, it makes little sense, but it's still been around in my mind. Another theory I had is that you (as in your soul) does reincarnate, as a sort of conservation of spiritual mass maybe.
I was a spiritual kid.