Let him stew in his own juices right now. The minute you confront, it changes the dynamic.
Ats, I agree with Heather. He knows how you feel. He will expect a reaction. He will prepare himself for how he thinks you will react. If you try something different, you will feel differently. This has probably my biggest 180. It has made me emotionally more in-check. (Yes, I know, it probably does not come across here... I save it for you guys. Lucky you.)
Two things about that: first when he told me (over phone) about hww and preg, he was definitely surprised about my reaction. He asked if I knew because of how I did react (or lack there of). Really, I think I was just in shock. But, it was unexpected for him and I think he had to think more about that.
Next, this has been hard on my parents. They have been his only true parents and have known him since a teenager. When they found out the latest development, I told them not to even bother talking to him. He knows he is wrong. He feels bad. But, if confronted, he would be in a position to defend his actions. Don't give him that opportunity. He knows it is hurtful and wrong. Let him think about that- what he is doing and not how you are reacting. He knows you are hurt and it's not what you want. You don't have to say a word.
Maybe I am way off on this. But I have fond that this works for me. I think it holds h more accountable for his own thoughts and feelings vs my emotions. During this time, he really is only thinking about himself and will say whatever to rationalize that. Controlling my reactions has helped me tremendously to be patient and to watch. I can focus on myself better. I am more in control. I can pay better attention to others' reactions when I am silent. Be patient..... the right time will come.
Oh yeah, I have also found that when I have wanted to respond/communicate- I have waited. I have written or typed the things on my mind and waited. Most often, it is never sent. When it is, it is usually well revised and sent much later. I had started writing something a couple months ago with the impending divorce. I was going to send it when things were closer to being finalized or after they were. I waited- boy am I glad I did. I was writing under false circumstances. What I believed to be true was so not the case. Be patient, my friend. Silence can be golden.
I don't know if this is helpful, but maybe some food for thought. Others with more experience may tell you differently. But whatever the case, you will get stronger.