Earlier quoted context omitted.
Tune me out if this doesn't resonate with you, but what you're describing, does it feel like it could have a spiritual component? Is it a sense of total, overwhelming hopelessness, but a rational one, based on existence as you can understand it? I spent a long time in a state like that, with suicidality and all. In retrospect it was a total "poverty of spirit", and I had to accept a drastically different understandin…
Did you turn to organized religion? I find that I don't really believe in anything enough (not just religion) to be a spiritual person. How did you develop a spiritual component?
Though to give some background, even when I was an avowed atheist, moral relativism was something I could never abide. I always felt strongly that as intelligent beings, there was truth and objectively better ways of existing to be found. The book "The beginning of infinty" helped me justify that rationally, and also made me realize how incredibly powerful, rare, and valuable intelligence is as a force in the universe. From there, CS Lewis' "Abolition of Man" got me onto the idea of natural Law, and the "Gospel of Thomas" got me thinking on the timeless, and somewhat subversive nature of the truths that Jesus taught. I looked many places, but found Jesus' teachings to be uniquely valuable to understanding the state of myself own soul. From there, it was a matter of choosing to believe him on the harder stuff (CS Lewis' Trilemma came into play there). The feeling of belief did not precede the decision to believe, which surprised me, but is apparently not uncommon.
I'm glad I did though, and my spirituality (which I only developed afterward) has become really essential to my life and hugely positive for my wellbeing. The organized religion aspect is more of a support system and framework to practice it in, but quite helpful nonetheless.