I started having these same feelings about a year and a half ago, shortly after my grandfather died. It made me so depressed and I started to view life in an entirely different way. It wasn't just the thought of non existence that scared me, although that was part of it, but also the exact opposite. The idea of living forever and ever also felt overwhelming. Even reincarnation, which I thought would be the best outcome, also started sounding horrible. Imagine if I was reincarnated as a gazelle or something and had to die a horrible death. I also thought about the idea of the universe resetting and having to live the exact same life over and over. Eventually, I came to the conclusion that every single possible after life sounded terrifying, and I started getting really depressed. I started becoming incredibly conscience of the fact I was getting older, and every day seemed to just slip by, as I inched closer to my inevitable demise. I just could not stop thinking about death all day every day. I actually for the first time started considering suicide, just to get it over with.
Nothing felt real anymore. Everything just felt pointless.
I tried coping by watching TedTalks about how you shouldn't fear death, about out of body experiences, and I even started looking into Aubrey de Grey and living forever. However, the thoughts just kept coming back.
In the end though, I just kinda got over it. It's kind of a pointless thing to worry about. I'm just concerned with living life to the fullest.
How old are you and how long have you had these feelings?