It doesn't make sense to people who haven't experienced it themselves, but sometimes the situation gets energy intensive to us that the only way to cope with it is to shut down completely. To the point where I've been sitting in front of someone screaming abuse at me and not being able to hear or remember a single thing he has said/screamed to me. All I remember from it is the unpleasantness.
On a bit of an unrelated note, how much time do he have alone? I tend to communicate better when I've been alone for a few hours.(Sleeping don't count)
He drives a lot for work, so he has time by himself in the work van at least a few hours a day, and as a hobby he plays music by himself and reads sometimes. I'm a very independent person, and we are not one of those glued-together couples.
We have tried e-mailing. I've given him written letters, too. I e-mail him sometimes, when I know it just kills him for me to verbally question him on any level about a touchy subject.
And what you said about shutting down completely is the only way to cope, is exactly what mhy boyfriend is doing. he has told me his way of coping is to shut down and not care. to the point where he doesn't care that he doesn't care.
I only came across AvPD for the first time when I was reading people's posts on this forum, maybe a few days ago. I looked it up afterwards to see if my boyfriend fit the bill. I'm not one to make a diagnosis or even hint at him that he may have this. The description doesn't seem to fit him too well, though. He's not a self-loathing person. When we are talking about our hobbies he seems like a normal, albeit shy and mumbly, person.