My ex has this. The diagnostic criteria don't give a clear picture of exactly what the disorder can be like -- he's abusive, unfaithful, misogynistic, emotionally unstable, arrogant, childish, and is completely obsessed with the idea of becoming a great genius. He also has no conscience and is unable to empathise with other people. Most importantly, he lacks insight into the fact that he is extremely disturbed, and believes that his behaviour is completely rational and it's other people who are the ones with problems.
Worrying about whether or not you're mentally ill is a sign of sanity. You may be envious and resentful, and have certain other personality traits that you're conscious of, but that's by no means pathological, and it certainly doesn't sound like NPD.