I'd agree with that advice. Don't bend yourself into a pretzel wondering what's going on with you and trying to self-diagnose. If you can get a diagnosis from a pdoc, particularly a clinically experienced pdoc, you will have the information you need to start taking steps toward improved mental health. Best wishes!
Well, I suggest the first step the be to schedule an appointment with a psychiatrist and therapist for evaluation and treatment. At 18 you are going to experience a lot of changeing and difficult emotions, but what your describing dose sound like something that needs to be addressed. I would also suggest not reading to anything, as that might cause you to self-diagnose and become more depressed and confused. Leave the diagnosing up to the experts, and read into the information they give you after you see them. I applaud you for reaching out for help, and this website is always here if you need support :)
Sara RN