Heatherfeather, in my experience there are different kinds of numbness.
I went for about 3 years never crying or reacting emotionally. But I smiled in the right places and made the right sounds. So a person would have had to have known me quite well to realise I was numb. So thats one kind of numbness that can go on for years, but I think people simply learn to live with it.
There's another kind of numbness which is where the thoughts and images of things that are upsetting, play out in your mind, but you can't connect emotionally to them. Then there are moments when the fear of what happened suddenly grips you. But also, there's a fear of realising that you are numb to it.
Then there's a state where no emotions show, I might seem cold and un-caring on the outside. And that's when others are most likely to think I'm numb. But those are the times when inside I'm anything but numb. It's more that I freeze because the emotions and thoughts flooding my mind aren't something that can be expressed coherently. And at those times, I know it sounds harsh, but the needs of other's who can survive without me, don't register as a concern. That's why I appear numb or cold.
I'm not sure if any of these will help you recognise what your husband is feeling. But I think it's important to remember that behind numbness are very powerrful emotions. It's rarely cold, as it might appear from the outside.