I would recommend self-advocating as much as possible. You know yourself and your mental experiences best. I am also age 25 and high functioning, but I have always been taken seriously and received treatment. Being high functioning does not preclude you from suffering. It just means you are strong and perseverant, which are strengths that should be considered along with your struggles. The therapist and pdoc should be basing the diagnosis on your symptoms and how they're interfering with your life.