Two years is far too long for your partner to continue hiding his past, family and ex-relationships. This has to be something he’s been doing for a long time, probably since he was a kid. You’re not going to pull down that wall overnight. This is going to take time, and you will need to be patient with it.
Sit him down and spell it out for him, tell him the emotional wall is an issue, and it has you feeling like you’re dating a stranger. And let them know you want to work together to break it down. Propose a 20-minute conversation each night when you both talk about your day. Ask follow-up questions, and if he tries to deflect, bring his attention to it.
If he wants to bring up something from the past, fine. If not, don’t force it.
To get through the wall, start with the present and move slowly backward. If you try to jump straight to the past, you’re only going to hit the wall. It’s a slow process, but it’s the only way.