Help Husband Cheated for years I need help.

I need advice. My husband have been married for almost 15 years. To give some history my husband and I dated for 3 years and got engaged, after getting engaged he broke it off. He told he cared about me but did not love me like a person who was going to marry should. I found out a month later I was pregnant. I told him and I guess I should have gotten a clue, but during the whole pregnancy he never came to see me. He was not there when our first child was born. After the child was 7 months old I traveled to the state he was living in and to show him the baby. We spent the day together and he told me to go ahead and plan the wedding that we would get married. I was so happy I thought we could make it work. We were married for a 4 years and he told me he didn't want to be married any longer, but I ended up pregnant again. After this he decided to stay. A couple of years after my son was born he admitted that he had a one night stand. I forgave him and I've tried to do everything I can to move on. About six years ago he started having an affair with another woman. After they had seen each other for two years she got pregnant. When the baby turned two he admitted to me that he had an ongoing relationship with this woman and they had a child. I told him that we would make it work. I tried contacting the woman, who will not call me back, and send her emails to try to make the child apart of our lives. Well fast forward I found out he's never stopped seeing her. I found an email that she sent him and she referenced bad things he had said about me and that he had promised to leave me to be with her. This has been going on for a total of 6 years. I did call her this time and told her that I wasn't going anywhere and she needed to leave my husband alone.  I told her I wanted to hear it from her that she would leave him alone and she wouldn't agree to this. She hung up on me and I've tried calling her back but she won't answer and I think she has blocked my emails.  They keep coming back to me.  He is still here and we just kind of pretend like nothing has happened. I don't think he has contact with her but i truly don't know. this is eating me up but I want so badly to keep our family together. I'm not sure if he's staying for our kids for money or what. I don't know if he loved her or still loves her. It's such a mess. I feel happy that he's home but I feel like I'm waiting for the next shoe to drop. What do I do to make this better?