Having the correct diagnosis can help with getting the treatment you need, for sure... but I want to gently recommend that you may want to try letting go of the idea of having the perfect diagnosis to explain your problems. No diagnosis is going to be perfect, human beings don't fit neatly into these little boxes. If I were you I'd just focus on finding solutions to the problems at hand.

I can relate to the sense of unreality you describe, I suspect that the root causes are likely very different but I know that is not a pleasant feeling.

A lot of therapists can definitely help you work through issues like excessive guilt, there's also quite a few articles written by psychology journals and such about this kind of thing that may also be helpful to you.

Best of luck.