Sarah, He may be worried about what YOU are doing now that he is with OW. Remember, thieves have the biggest locks on their doors! As much as they say they don't care what you do they actually do. He is cheating and knows you know it. If he can, why not you? It would also be good in a way as he could say you are to blame if he could "prove" you were up to no good. Remember, he wants you to be the "bad guy" so badly!
My W found a post I made on another web site back in December before I found DB. Nothing on any post was "bad", just the truth and my W used this as a "reason" I was to blame. She said I said that she was up to this or that, which for the life of me I don't understand as I never posted anything like that! Who knows, she could have been reading someone else's post and just thought I was the one who wrote it! The worst part is she waited months to tell me about it! She just stewed and made it more and more than it was. They will take whatever they can and twist it around to make us the problem. No need to say anything to me about it or ask me or talk to me, that would have defeated the purpose as I may have been able to say it wasn't my post.
They know what they are doing is wrong at some level. They want you to be wrong as well. If he could find something that would be all the better.