I had a psychiatric break around 2015 and couldn't focus enough to read a book. That inability lasted a few months. I had depersonalization and memories of my past were dreamlike. The memories either felt unreal or were disorienting as if I was being transported to a previous time. I also had some strange physical phenomena, much of which I probably forgot. What you're experiencing is strange, but it's important to try and calm yourself and forego self-analysis for a while. If you were calmer and not analyzing yourself you'd perhaps not be experiencing any of these problems. Some people on this site have depersonalization from physical issues but most haven't identified a physical cause unless you count marijuana. I'm not a doctor but I recall the most standard tests are blood tests for things like vitals, vitamins, and hormone levels. If you have good results and no other physical symptoms they might prescribe some rest and relaxation or refer you to a psychiatrist.