Thank you all. These replies are so helpful. I woke in the night and thought about them a lot.
While I maintain that the first response wasn't hugely helpful - defensiveness is engrained, and it's not that easy to stop it/grow up - it did me a massive favour, because it does illustrate how quick I am to react.
Clearly, my problem is reacting instead of responding. It probably always has been. I don't pause enough. I don't take a step back. I liken my response to the first reply a bit to how I used to reply to email - very quickly, as if I was totally sure of what that person was saying to me. In fact, often, on reflection, what was being to said to me could be taken several different ways.
So, essentially I always hear criticism. And my antennae is so heightened, that it pings before I even have a chance to consider that a) it's not necessarily criticism, it's just an observation b) even if it is, is it really that big a deal?
I think I probably have very low self-esteem in some ways, while being very robust and quite a brave person in others. I am very hard on myself. My critical voice is very strong and I'm probably expecting it from others.
My husband isn't abusive. He's a top person - very kind and generous, a terrific dad, and a very very supportive partner. I also have some good traits, and we have a pretty fab life together. There is lots of love and laughter.
For the purposes of this thread, the bits that need highlighting are:
He's also difficult to live with (his words), hypercritical (his words) around stupid small, often domestic stuff (his words) and can undermine me (his words). So, it pings my already established antennae.
I'm a control freak with a tendency to want to take over - which irritates the shit out of him, understandably - and i have a fiery temper and knee jerk reactions.
Strangely - and perhaps this is all part of this big growth I am undertaking, and need to take - I've done a lot of work on my parenting over the past few months in this respect. One DC is particularly wilful, probably far too much like me, and pressed all my buttons. I would react, lose my cool and then feel awful. And as a team, DH and I undermined each other, and the DC in question, manipulated the split. I sought parenting help, (for me, as as a team) as I really wanted to become a better parent, and although it is early days, I've been working so hard on walking away, not engaging, etc etc and it's been great. Ace. Much, much better between us all.
This is clearly what I need to do with DH, but for some reason it's much harder. I probably feel less responsible for him, for his feelings, if that makes sense. And we've been together a long time and patterns are seriously hard to break.
But I want our marriage to survive, which is why I'm here. I want to shed this shit! It drives me mad about myself.
To the poster who ask if I have lots of run ins - no. I get along with people well, have some wonderful friendships. I don't have a problem with confrontation but I don't seek it out.
To the poster who asks 'what on earth do I have to be defensive about...' etc, it's just not a logical thing. It's not rational. It's a protective mechanism which you don't think about a lot of the time. It just is. It clearly had a place in my past.
Ironically, work wise, I am in a profession which relies on having the skin of a rhino - needing to rise above constant criticism and subjective opinions and rejection - to get anywhere. I'm pretty successful.
Without shifting any blame elsewhere, I grew up in a family, and culture, where tensions, passions, anger could run quick and high...and then simmer back down, as if nothing had happened, all in the space of ten minutes! It sets a template. But it's not a healthy one.
What is clear is that although I would like him to work on his stuff, I must take full responsibility for mine and if I change, he will follow.
There. I've tried to be as honest as possible.