Heya @Thisgirlwantstosleep,
I suspect that what you are experiencing is another aspect of SI - SI is so incredibly strong and insidious.
With respect to reincarnation, interestingly, my sister, at the age of 3 or so, used to talk about her past life all the time. Now, this was in the mid 70s, and my parents were very religious and never spoke about other religions - I don't think they even knew about reincarnation. Also, at that age, the only access we had to outside or different viewpoints was a very small black and white tv that had about 3 channels. Odd thing is, my sister is what some people would call an "old soul," i.e., wise beyond her years.
However, this does not constitute proof of reincarnation in any way. My mother may have been lying for attention (common with her), and sadly, so many people crave attention, it would not surprise me that others do this as well. Also, there has been no scientific evidence to support reincarnation without a shadow of doubt that I have observed to date.
However, suppose for a minute that reincarnation does exist. Who is to say that the pain of this life is not a learning lesson that leads to a better life in the next incarnation (aside from one particular religion - and religions IMO are nothing more than modern-day accepted cults)?
The thing is, we do not know and will not know until we die. And everyone will die one day. So, in my opinion, it is not worth worrying about now or letting SI latch onto you - if it is in fact yet another aspect of SI.
Also what some here have said about the brain is spot on! I have had at least 4 severe head injuries in the past 10 or so years (this does not include what I sustained as a child), and I am not the same person I was before these head injuries - other examples of this would be dementia-related illnesses where the ego or sense of self disintegrates and is lost over time while still alive.
Please know I am not encouraging suicide, just hopefully giving a different perspective on life and death than what many are typically taught.
Much hugs and love to you, that feeling of terror in any situation is beyond awful