Call me Crazy

So earlier this week my husband confessed to me that he still think about his ex ( basically still in love ) so he offered Marriage counseling. I dnt see how marriage counseling could work bc we dont have a problem, our marriage is great. honestly if he never said anything I never would have known. So we talked and I gave him an ultimatum. I told him I'm not in the business of keeping someone who dont want to be kept. His thing is he's only THOUGHT about her and hasn't acted on it and I went TF off. He said that I overreacted. what are you thoughts ?