What should I do? I don't want to be a bad woman.

Since he is sincere, why did he leave you to get married like lightning? I think you should leave him as soon as possible. Maybe you will miss him at first, but it will get better after a long time. As you said, you don't want to be a third party like other people's marriage, but you didn't mean to. He has a good relationship with his wife on the surface, which only shows that he is an irresponsible man and spends as much as most men. And his current wife, instead of tying his heart, tied him with conditions. Such a man is not worthy of your love. It's not your fault. You should cut off everything related to him.