Taken from wikipedia:
"It has also been suggested that narcissists have two layers of rage. The first layer of rage can be thought of as a constant anger (towards someone else), with the second layer being a self-aimed wrath." This sounds very familiar.
I feel I'm in the same situation as you, I get these thoughts as well, not even just "saying I have these thoughts for attention" or whatever, but real borderline-eske ones. It may seem unusual to an outsider that we get these because we don't usually seem to be overtly depressed or emotionally unstable. Most of the time we seem kind of non-nonchalant and chill actually. I mean I truly thought I had BPD for the longest time, but I don't think BPD is as linked to negative self-esteem as it is in CNPD, so there's a distinction.
My version of having this seems to stem from some, vague yet deep-rooted underlying self-esteem issue; things I deeply hate about myself, things I can't accept about myself, or have anyone else imply them about me (i.e. defensiveness) because it's too threatening to my self-concept. If that makes sense? We usually like what's on the surface, not so much the "thing" we are underneath.
Before I even found out about CNPD I always had thought narcissism was all about mega ego inflation and very high self-esteem, but then I started reading about it and discovered there was two types, and it's the covert that secretly hates who, and what they are, so they develop some sort of self-protective second skin to live through instead.
After reading through the forum for a while, one or two users suggested we may have been confused with borderlines at one point, and I think this might be true, you know, unstable on the inside but protective narcissism on the outside.