OW was probably freaked out because she was afraid her cover would be blown. Affairs are like iceburgs. You are only seeing the tip.
You know what, I freaked out when I got married. We dated for 4 years then in like 8 weeks, we got married, bought a home, I bought a car and started a new job. Once the dust settled and the excitement was over, the realization of "this is my life" hit me and I wigged out. I didn't have an affair or anything but I was quite depressed over all the options suddenly disappearing. I totally dug my wife, house, job, car etc... BUT now you are IN, for keeps. I felt a similar sort of anxiety when my first child was born. Maybe your husband had a crises, maybe not MLC but some kind of crisis. He clearly loves you but men are weird. The finality of actually marrying might have messed his head a bit. FWIW, YMMV and all that stuff.
Me 44 She 46 S13 D9 M18 T23 3 years DB'ing Successfully busted