Judging by your response, then, yes - it is clear to me that you are having a tremendous amount of ANTs about not just blushing, but your self-worth, self-accepance - the same ANTs that develop for most of us with social anxiety.
It's not hard to understand how we get to this point. Perhaps through some long period of stress or a negative environment, perhaps because of something traumatic that happens, maybe an event that occurs that embarrasses someone and becomes a flashpoint - no matter what it is - we develop early on a learned pattern that only strengthen over time. And the longer this seed grows into a plant and into a stronger tree, our opinions and thoughts would naturally only become more negative.
You may have been more secure in a certain position of your life, not necessarily having to face certain kinds of stress and thus more self-assured. But then things change and all this stuff comes back, although it was never really gone. So, again, for anyone reading this, anyone who may relate to this experience - I tend to doubt when someone says "It just comes out of nowhere and there's no reason why." With blushing it may feel like that, sure. And we are all along a continuum of social anxiety at different points. And we are all different people with different personalities, as you can see right here with lizzy45. One person with social anxiety might actually be an extroverted social butterfly, and another person may be a quieter, introvert - I mean their natural personalities - NOT what social anxiety does to them. Social anxiety does not determine your true personality, except that it can smother it and keep it down so that you begin to wonder who you truly are...
Back to the point, I don't generally think that this feeling, this symptom comes from nowhere. Yes, it feels that way, and it is such an uncontrollable rush that seems to the person to be automatic. But, as you say lizzy45, in fact you had blushing issues at earlier periods in your life, and you describe all the ANTs associated with others judging you, what you think they are thinking, which actually points to some amount of self-judgement and self-rejection. A negative view of this thing that is happening to you, which also usually leads us to resist and fight against it, leads us to hating ourselves. This description of yourself having a flaw that people would then know if they saw you blushing, especially when otherwise you are quite a "normally social" person - this is a common thought around blushing. "If people see me blush, they'll realize that I'm not as perfect as they thought I was. If they see me blushing, they'll know I'm defective, a loser, a weirdo." However the person says that in their thoughts, this is generally the ANT that comes out of that.
Without going further here, the answer is still the therapy for you, and for anyone reading this who is interested in this particular problem.
Slowing down, deliberately practicing slowing down, calming down - this will be very important here. Practice your slow talk daily, as we all should. Practice going slower than you think you should. You will need to practice this. The way we can move these skills into the real world is through practice during therapy time. Then you slowly use this with easy first steps, like family members or friends. And slowing down may not come as easily to you here because you do have such a quick trigger on this adrenaline. Don't get mad about yourself not slowing down in situations. The "not getting mad part" will be emphasized in later sessions. In short, we never want to use a negative emotion when choosing to stop or get away from anxiety. Resistance of any kind just serves to keep the negative feeling alive.
And secondly, be aware that you very very very likely do have ANTs about blushing. It's not a tornado that comes out of nowhere. It started due to something. We don't always have to know why things start. But, we do have to be aware of our ANTs. We stop them, label them, try to start not paying them as much mind, and ultimately you try to start making them neutral and then more positive, realistically.
I could go through each ANT in your writing above and give a very rational neutral counter, which in my mind would be real, true, not an ANT. I could do that, but it wouldn't help you believe that. You can do that for yourself. Read what you have written and identify the ANTs, and then be rational. Be good to yourself. At least be neutral and see how perhaps what you are saying is maybe not true, maybe a bit too negative, maybe not justified. Everyone has problems in life. Everyone knows what it feels like to not be perfect. Everyone is trying to get through challenges and struggles. Everyone knows that life is not always a success story. Every success story is built on a bunch of failures. Every success story might only be a success because we say it is. What if that success story is achieved by someone who feels they are a fake? Maybe that last sentence is not a good neutral statement, but my point with that is that why even define fakes, successes, weakness... Why define those for our purposes. Someone will come along here and counter me with ... NO NO NO, of course we have failures and successes in life, blah blah. Again, I'm not talking about other parts of necessary life. I'm talking about what we do to ourselves and social anxiety, and really another side of truth which is real - even a failure to someone can be a success to another person. And what is it about you that you are calling fake, etc? You are a human, you exist tangibly. You go through this world as I do. You're not faking being a human, right? All humans have struggles. Perhaps we don't have to define our struggles negatively.
Anyway, you get the idea. You have to do this for yourself. I can't do that part for you. I can't do the daily work and repetition. I can't make you believe about yourself what I already believe about you, what I know to be true, even without meeting you, because at least I know you are a human being, so all the things I've said are true for each and every one of us.
Open yourself up to these therapy ideas. Don't get mad at yourself when you have setbacks. There is more to come in the therapy, and you will start to see how the different pieces all fit together.