Ex came back and then left again

My ex came back to me after months of no contact. We ended things on good terms and we still loved each other when we broke up. He was very loving toward me and I could always count on him. When he came back he seemed different, almost a bit off in a bad way. He was a bit meaner and sometimes would do things to offend me. Then he just left and won’t talk to me anymore. I feel really hurt because I never thought that he would ever do something like this to me. It will help me move on, but I’m just so sad about it.