I'm not a partner. I probably shouldn't answer because I might just be mudding up the water. But what I feel when I read the above is shame and inadequacy. (maybe just reading my issues into your post) Maybe he got hurt but really knows that it was not a big deal other than to him. Maybe he doesn't want to open up to you because he feels inadequate. Opening up to others is possible because he doesn't have to live up to the ideals he has set for himself in your relationship.

Opening up to you may be too scary because he can't take it back or run away from it. He still needs protection from being hurt. Nobody else can hurt him like you can because they are not as important to him.

Compassion means putting your heart out and if you are too scared of it being broken then you won't.

Like I said, maybe just my me reading what I feel into your situation. Might be the right answer to the wrong thread.