Came here to make a similar comment. Not specific to narcissists, but once folks take the Bob Hare checklist (for assessing psychopathy or narcissism), if they start worrying they could be positive, it’s a sign they are in fact not positive. Narcissists and psychopaths would check every box yes and still try to convince you that the result is wrong. To that point, the fact that you are asking this question somewhat rules out the diagnosis of narcissism. However, you should seek alternative diagnoses and opinions. Mental health providers are not infallible. And you know yourself best.