Sorry to hear about your H's sleep talikng. In reality, this is to be expected in some form. Meaning, he had some form of attachment to the OW. As with any form of addiction, he is experiencing a form of withdrawl. The addiction provided a form of excitement, secrecy, thrill, etc... that he is now withdrawing from. I want you to know this is totaly normal for your H. The positive of this is, it is WITHDRAWL. The beginning of the end. The other positive is, it is just words. You are able to SEE his actions. Observe those far more than words.
I understand how this hurts.(you posted at 1 am!) Any mention of OW is going to cut to the bone. I would suggest you talk to him about this. When you decide to, make sure you are in the best emotional place you can be. Rehearse a couple of scenarios through your head. Try to anticipate his responses and then your reaction. This will accomplish numerous things. 1. It will let you communicate to him how hurt you are when the OW is mentioned. 2. You will be able to get this event out in the open and not keep the intense emotions associated with it inside. 3. You will get to see the actions he portrays to you when you discuss the issue. and 4. It gives you a great opportunity to show him your strength in wishing to discuss the most difficult issues. This will be a valuable tool for both of you as you reconcile your M. No matter the sensitivity of the issue, get it out there and come up with a solution together. In short COMMUNICATE.