I'm almost certain I have narcissistic personality disorder
What makes you feel so strongly?
Their need for attention, their sense of annoyance, submission, aggression and friendliness.
It's always wrong to self and armchair diagnose because you are not a professional. But, since you do highly suspect that something is wrong you should go ahead and get checked. You don't want to walk around saying you have something you don't.
I know better, it's not like I need to go to a doctor to find out what I want to know.
The doctor might be able to help you with you symptoms though. I think that if you are so sure that you have a disorder, you should have a doctor evaluate it.