Not being able to communicate with a person you see as a potential life partner, would be a very poor beginning to a long-term relationship. You can try to open him up to perhaps unloading some bad memories from his past. If that's not the problem, look to see a therapist together. All that I am suggesting is a not-so-good way to begin a life together with another person. But, a therapist has been known to help in some cases. You should see this, with your eyes wide open, as a red flag. A person that is open and communicative, or closed and shallow, is generally considered a character trait developed over several years...usually from early stage childhood...someone like yourself. Much like someone with a hot temper, you know it's going to be a huge challenge, with much trial-and-error to get this person to change. That problem, not able to communicate, (by holding everything in,) borders on emotional abuse to the other person, which usually ends a relationship. If children are involved, it would be that much more difficult to break from that, which is considered, a dysfunctional relationship. As a mature individual you should think long-term; would you want your children being subject to the same unhappiness your feeling when you experience, head on, a person who can't for whatever reason, communicate?