Hi denmu. I found myself going through something similar recently. We are 15 months post d day. My mind was going around in circles, and I was restless, still looking for answers. I found myself spending a lot of time thinking about whether he's really changed and reading blogs and sites like these.
I talked about it with our MC and she suggested I designate 1/2 hour a day to thinking about the affair. If I have thoughts /worries at other times, I either save them for later or write them down to think about during my 'worry' time. She explained that worrying /anxiety is behaviour, and it was my choice whether I do it or not. And I'm far enough down the line to know that whether I worry or not, I can't change things.
It's given me the headspace I need to stop thinking about things all the time and enjoy the moment. Plus I'm able to get more work done and spend more quality time with my kids.
It sounds very simple, and I was in enough of a negative thought spiral to think it wouldn't help, but it really has. It's been a week since I started and I'm so much calmer.