Hi Ruby Rae,
I can relate to what you described. I do better at managing when I know what the trigger is. I hate it when I slide into a downward/depressing ptsd cycle and I have no idea what triggered it to happen. It's taken me a long time to slowly figure these triggers out too. I can relate to having the negative thoughts about life and not wanting to deal with it etc.
I recently posted an article that talks about how the brain is affected with PTSD. Did you get a chance to read it?
Here is the article:
https://www.forbes.com/sites/quora/2.../#1f70f79b5eaf
Keep in mind that a memory flashback can consist of an emotional memory that you may not understand exactly what it's about. The conscious mind can get confused because the connection it has with the amygdala is not what we think it is.