With this kind of deceit...please prepare yourself for the response...this level of hiding is never good...

I don't think the question is "Why would he jeopardize his 20 year old marriage simply because he thought I was jealous or because I would be upset at his seeing her?"

I don't think it will have anything to do with he didn't want you to be jealous or upset...

I'm sorry you are going through this...you may want to talk to a therapist to help you sort through all this...