When she was growing up, the writer Lindy West was bombarded with negative messages about being fat. The whole world seemed to think she didn’t deserve love unless she lost weight. In her first book, “Shrill,” West wrote about how hard it was to combat fatphobia within herself, in society and on the internet, where she was attacked by some particularly vicious trolls. By the end of the book, West had found confidence in herself. She also got married to the love of her life. Now, West is opening up about a conflict that was built into her marriage from the start: She wanted to be monogamous. Her husband, Aham, did not. To make Aham happy, West agreed that he could see other people, but she was terrified of what would happen to her self-esteem if he ever acted on it.  This week on “Modern Love,” West talks about what happened when Aham started seriously dating someone else. Once this new girlfriend entered the picture, it forced West to rethink her feelings about her marriage, and about herself. On the other side of all that tough emotional work, she was surprised to discover a new kind of joy.  Lindy West’s latest book, “Adult Braces: Driving Myself Sane,” comes out March 10. Subscribe today at nytimes.com/podcasts (http://nytimes.com/podcasts) or on Apple Podcasts and Spotify. You can also subscribe via your favorite podcast app here https://www.nytimes.com/activate-access/audio?source=podcatcher. For more podcasts and narrated articles, download The New York Times app at nytimes.com/app.