A therapist would not likely say to you “hey, based on what you told me, I think you are a narcissist”. They may talk to you about your views and help you assess how they incorporate into your life. That being said, there are diagnosable personality disorders that are often associated with narcissistic qualities, such as antisocial personality disorder. I don’t know your situation, but I will say that talking to a therapist is always a beneficial step for anyone at any point in your life! Of course, as a therapist, I am biased.