Welcome to MS. What goes on inside a survivor's mind? Well, it depends on the survivor, but some of the commonalities that link the men here are lack of trust in anyone, particularly figures of authority, histories of drinking/drugging and acting out sexually (and a host of other behaviors), a pervasive and persistent sense of unreality, isolation, numbness of feeling and emotion, persistent and pervasive fear and anxiety, depression, emotional overreactions, physical overreactions, the list goes on and on and on. Are any of these issues for your S/O? Could be, but he's the only one who can say.
I am sure it does hurt when he doesn't feel like sharing. All I can say is that if you're patient and don't push, that may change. It may take some considerable time, but the possibility for change is there.
In the meantime, you may want to take this question over into the "Friends and Family" forum -- the women and men who post there can probably give you a lot more help from their experiences as supporters and partners and spouses and friends of survivors.
Keep coming back, it sounds like you've found the right site.
Take for us the foxes, the little foxes that spoil the vineyards; for our vines have tender grapes. Song of Solomon 2:15
But let justice roll down as waters, and righteousness as a mighty stream. Amos 5:24