A general pattern I've found when it comes to unwanted compulsive mental attitudes and states is that they are compulsive because the alternative is always worse and undesirable to the person in some way. For instance, a pervasive "fear of control" is compelling because that attitude of being in control is much more uncomfortable for some reason than feeling perpetually powerless.
The basic mechanism is that your current pervasive attitude, no matter how much you believe it's unwanted and undesirable, is compelling precisely because it is beneficial to you in some way. But how can low self-esteem and being afraid of people's judgements be beneficial? I hate being this way, it's so painful!
And yet, it's much less painful than the alternative. Think about what a "normal" person does when faced with real or imagined negative criticism, their ego defense mechanisms turn on, they invent a story or justification and they don't budge, because it's emotionally painful otherwise. That instinct is the default one and everyone has it, but in your case, you have labeled it as unacceptable, put up an electric fence around it and you are dissuaded from using it through even emotional pain.
The reason you are so sensitive against negative judgement is because you are defenseless against it. The attitude that would allow you to deal with negative judgement is barred off and unavailable to you. If someone attacks you, you can't get angry and defend yourself, whether verbally or otherwise. if someone says something negative about you, you can't prove them wrong, stick up for yourself or just tell them to fuck off.
There's an exercise that let's you bump into this mechanism on your own. Try to imagine what it would be like to be confident, self-assured, to dismiss other people's criticism, to believe you are worthwhile despite what other people say etc. imagine actual concrete situations where this happens and you take up an attitude of confidence. Notice what happens, do you feel better? Maybe for a bit, but then you might get a sharp pain that throws you back into vulnerability or something else is not right, some other reason why this attitude is not allowed or deeply uncomfortable and unwanted.
The emotional pain is usually deep shame that needs to be released and transformed. Once you get rid of the "electric fence", that attitude of confidence suddenly becomes available to you and you will remove your sensitivity to negatiPost too long. Click here to view the full text.