I know how you feel. I was with my ex for four years too and it really hurt that he seemingly took the break up so well while I was absolutely shattered. I try to remember that he is an alcoholic and that relationships don't mean the same thing to him as they do to me. His primary relationship was and still is with alcohol.
Your ex is recently sober so it makes sense that sobriety is all he can care about right now. I know it still hurts, which is why I have to agree with everyone else and recommend no contact. It is too hard to heal when the wounds are repeatedly reopened. I have had contact with my ex a couple of times since we broke up six months ago, and absolutely nothing good came of it. The last time consisted of a few emails only but seriously set me back. NC is scary, but have faith, it really works!