You have asked some very good questions. People can have multiple disorders all at once but I do not think it is possible to have all of the disorders you listed simultaneously. You have experienced what research shows to be true, which is that diagnosing mental health disorders is not an exact science. Studies have shown that when presented with the same set of symptoms doctors trained to diagnose mental health disorders often do not come to the same conclusion. That means that three different doctors might diagnose the same individual with the same set of symptoms with three different diagnoses.
Another reason that you may have had many different diagnoses is because our understanding of mental health disorders has substantially changed over time. For instance, 30 years ago, it was commonly believed that schizophrenia was caused by an overbearing and strict mother. New research has discredited that theory and now it is thought to be primarily an organic disorder. Relatedly, dissociative identity disorder (formerly multiple personality disorder) was confused with schizophrenia, even among professionals trained to know the difference. DID, while still not a fully understood disorder, is recognized currently as being distinctly different and completely unrelated to schizophrenia.
After many different diagnoses from many doctors, I understand why you are unclear about what your “real” diagnosis is. It’s possible that you have a variety of symptoms that do not fit any specific psychiatric diagnostic category. It is also possible that your symptoms simply do not warrant a mental health diagnosis. That is why I would advise you to focus less on gaining a specific diagnosis and more on finding good, quality treatment. Treatment is what matters the most. If you were to find a therapist or a doctor who could effectively treat your symptoms then your life would likely be significantly improved. In some cases and with some disorders “cures” are possible, but a more realistic goal is finding a competent mental health professional or set of professionals who can help you live a better and more satisfying life. I hope you are able to find that type of help. You can start here by searching this directory. I wish you the best of luck. Thank you for your question.