Hi and welcome! I read some of that book, it was a heavy read! I was formally diagnosed in 2017 but previous therapists had suspected it. My psychologist did most of my screening tests (some questionnaires to fill out and her observations over time) and then I had a formal 2 hour diagnostic interview thing with my psychiatrist. I received a copy of the full written report from the psychiatrist later, it was pretty harrowing reading seeing it all there together!

Since then I've been working with a trauma therapist and I feel like we've made a lot of progress... definitely more progress than I've made with any other therapist now that we are doing the right things to help with the real issues.
Welcome to the forum.