Help! My husband is leaving me to live with birth mom

My husband was recently reunited with his birth mom 3 1/2 months ago! They were calling and texting each other non-stop, and I didn’t know that this was normal. I harped about setting boundaries. He didn’t. He told her. She ended up hating me. They wanted to meet each other alone. I said he needed to include me. I harped and harped and pushed him away. By the time I figured out it was normal to have a honeymoon stage, he had sat me down telling me he wanted a divorce and that he was moving in with his mother. I told him I would no longer restrict him. I would be supportive. I now know it’s normal. He says he wants to live with her and that I am too controlling. What do I do? Why would a grown man want to move in with his mother and give up on a 23 year marriage with someone who is willing to admit their flaws and change to move in with his mother he has only known for 3 months? What can I do?