Don't jump on me for this, because the terminology is really really unhelpful and will sound like I'm insulting you when I don't intend to, but it sounds like as a form of self-defence as a teenager, you've had to develop some traits that aren't helping you any more, and which sometimes get described with the word "narcissistic".
I'm not mentioning it because I'm in any way qualified to diagnose a serious set of difficulties like those that get diagnosed as "narcissistic personality disorder", or because I think you have that disorder, but because I think there might be bits of the thinking patterns you describe that are similar to some bits of those patterns described by those disorders, though of course they're more serious, pervasive and persistent in a personality disorder.
Basically, there's two very different types of people who get picked up under the narcissist label. The ones who think they're amazing and deserve way better than everyone else (grandiose narcissists), and the ones who don't like themselves and feel inferior, but cope with that by trying to convince other people they're great, so that they get bolstered by a bit of approval and reassurance from others (vulnerable narcissists).
That leaves the latter group really vulnerable, because any time they don't feel like they've been successful in making people people think they're great enough that it compensates for their own feelings of being awful, or they're alone so not getting any input from others to balance out their own feelings about themselves, they're left with their crappy feelings about themselves, plus maybe the feeling that others have also evaluated them and found them wanting.
Unfortunately, unlike most traits where having a label to Google for will help you find info and resources for dealing with that problem and related issues, it's really hard to use the label "narcissistic" to find resources aimed at people with low self-esteem who have picked up this particular unhelpful coping technique. (It's mostly stuff for people who have armchair-diagnosed their evil parents or their horrible cunt of an ex-husband as narcissists, and need help recovering, TBH.) It is possible to find the odd thing, but you have to dig through a lot of stuff that would be pretty upsetting if you were to think it applied to you. I've heard good things about mentalisation-based therapy and schema therapy for this sort of thing, though.