I am not in your marriage, so it is impossible for me to really understand what it is like. But it sounds like he is getting back at you, perhaps subconsciously? He sounds like he really cares for you, wanting your happiness so much over the years. Even so, it must feel so great for him to have a gf of his own. Perhaps he is doing what he felt you were doing to him?
I would give him a break, he is new at this. NRE is powerful and stealthy. Giving him a break doesn't mean not communicating though! I would sit him down, have a serious conversation with him about his actions and how they are making you feel. Then perhaps, compare it to how he felt for the past few years. Just be there for each other and talk about your feelings.
I am in a similar position, as I pushed for poly and am the only one dating right now. I keep pushing my husband to get a gf, but he is only partially interested. I check in very often with him, making sure that he is alright with the way things went that week. It can be hard.
Have courage to continue this journey, for it holds nothing but lessons and wonders.