Hiya ChiTown. I hail from up that way (NW 'burbs) too. I'm sorry you're here.
I would be willing to bet that OM is putting pressure on her. It's a very common scenario for the cheating spouse to be withholding sex based on some internal "line-in-the-sand" that they have morally. It could be the day the divorce is final (wouldn't that be nice), or it could be the day it's filed, or perhaps something else, but it would be some point at which she would no longer feel like she was betraying you if she got physical with this guy.
They may have even gotten physical already, and she may have told him "that can't happen again while I'm still married." You know us guys -- we can be pretty persistent.
If you're not ready to divorce, there's no reason you have to be as quick and agreeable as she wants you to be. Simply tell her "I'm not ready for this yet, and want to wait."
As for the marital bed, I suggest that you get back into it 100% of the time. If SHE'S not comfortable with you next to her, then SHE can leave.
Be prepared for her to scream bloody murder at both things, though.
