All responses really appreciated and helpful. It may be also helpful for me to give more detail.
He has never been abusive to me. He is very kind and gentle. We have our own kids who are both 18 from previous marriages but none together.
This is how things happened in a bit more detail.
He had major trauma occurred at age 16 within the family and was hospitalised for a year on and off for mental health support after it caused a breakdown for him. I am the only person on earth who knows that about him.
At his lowest ebb and only 17, he got into a toxic relationship and she was much older and also a bit abusive by the sound of it. Things like refusing to let him go out alone, trying to stab him on one occasion, using their child as leverage and blackmail.
He managed to get away from that and studied and worked hard and became a doctor, but then got involved in another relationship. This time it was seriously abusive. Hitting him, threats, coercion, emotional abuse, blackmail and he formed some kind of stockholm syndrome or cult-like sense of difficulty leaving this woman who had completely isolated him from everyone else. He finally left her the police had to get involved.
All all these people convinced him their abuse was his fault, which he still believes to be true. He came away feeling the world was extremely unsafe and very much permanently living in survival mode.
In the first two years I knew nothing about this. I am very tuned in emotionally with things and thought maybe he'd been hurt and was avoidant in his attachments, but definitely didn't see signs of major trauma as he was good at covering it and never told me. Like @scarpa he thought this would push me away and didn't want to risk it.
He was always loving, kind, reliable and we fell in love and got on great. We argued very, very rarely then and it was usually just a little tiff with no shouting or unkind words and it never lasted more than a few minutes.
Then 18 months ago the very abusive ex reared her head back into his life and began to threaten him. For example, she told him she would tell the medical board that he had assaulted her to get him to lose his job if he didn't meet her for a "closure" chat. Then she began more or less stalking and harassing me and it was pretty scary.
This went on for a few weeks and then he had a mini breakdown during which he told me the whole story. He was in his breakdown for about 6 months and it was pretty bad. Lost a lot of weight, was in a very bad way. It was a bit like the floodgates opened and he told me everything and said he was amazed I still loved him now I knew his past, which he thought was all his fault. I told him it wasn't his fault and asked him to go to counselling then, and he did for about 8 weeks, and then his counsellor got long covid and disappeared for a few months and by the time she came back he had clammed up and no longer wanted to talk.
I've not acted as his therapist (I don't think!) but I have done everything I can to help and support him. He's now functioning at about 60%, and we argue, which we never did before, because of the strain of it all and because, well, extremely depressed people can sometimes be snappy, mean, selfish and negative in a way that you can't comprehend unless you've lived with it.
I don't think I am a loud shouter, but me getting angry or upset in any way triggers him and he can start shaking. We have had to leave the cinema if the film gets violent. He has had night terrors. He flies into an absolutely massive panic over small things.
For example, I flippantly joked during a conversation about an awful day I was having that I was going to "shoot myself" and he raced home from work in terror that I was in danger, when it was obviously a flippant comment and I was completely fine.
He can also be paranoid, for example, now he has told me all his secrets, when we argue he is paranoid I am going to leave him and use the information I have to ruin his life - which is what his crazy ex threatens to do. No matter how many times I reassure him I would never harm him in any way, he just reacts to me as if I was her.
He is terrified of counselling, which he thinks might "unravel him" completely and then he will lose his job and end up alone because I will leave him and so on (?!) and he can't do anything like journaling or meditation for the same reason.
He is kind and loving to me and days or even weeks go by where we are normal and happy, but this is under the surface and I know he has to fix this in himself to be healthy and it's hard to watch such a beautiful person I love so much suffer like this.
EDMR sounds really interesting - can anyone tell me if you can have it without having counselling first?
He is also willing to read books, and he has read several on trauma, PTSD and also watched lots of YouTube videos on abuse and so on and he is slowly beginning to learn. He is so earnest and lovely and wants to be better but he's frightened.
It is also hard to live with, and as many people say, the refusal to go to counselling (at least for the time being) is very hard and frustrating. He gets overwhelmed and can't stand loud noises or crowds and he gets very tired.
From where we were six months ago is a vast improvement. He is loving to me, things are not awful. I just want to get a grip really of what I can do / need to do and the future. I sometimes feel lost a bit.