The idea that your life flashes before your eyes when you die is a common belief or hypothesis, but it is not scientifically proven. It's often described as a near-death experience (NDE), where individuals claim to have seen their life events in rapid succession during a life-threatening situation. However, the nature and validity of NDEs are subjects of ongoing debate and research in the scientific community.
As for the idea that you might already be dead and rewatching your life, this concept delves into the realm of philosophy and existential pondering. It is akin to questioning the nature of reality and the possibility of living in a simulation or alternate reality. While such ideas have been explored in various forms of fiction, including movies and books, there is no scientific evidence to support the notion that we are currently rewatching our lives after death.
In our current understanding of reality, we experience life in real-time, and there is no concrete evidence to suggest otherwise. The perception of time and consciousness remains complex, and it's a topic that has fascinated thinkers and philosophers for centuries. However, the best approach is to focus on living in the present moment and making the most out of our lives as we experience them.