I am also the mother of a 13yo son. He still has a lot of anger, even though his dad and I have been separated for five years. I've learned not to push things with him. If you pay attention, he will say things to you that will open the door to a conversation--when he is ready. FWIW, I think it's okay to show him your emotions, but just because you feel like talking about it doesn't mean he does. So, share with him how you feel, especially if your behavior is affected, but leave it at that. Also, take care not to make your feelings his fault, or his father's fault. Children will always imagine that things are their fault. Make sure, if you do share, that he understands that your feelings are yours and not to be blamed on anyone else. The example of taking responsibility for how you feel is more valuable to him than "getting him to talk." Especially if he's not ready or willing.
L