Hero and heroine separate after meeting in highschool, heroine is plus size

[Inti]

Hero is popular and mean to Plus size heroine in school. They later end up dating but hero's father disapproves of their relationship and doesn't want to pay for Hero's future school. Hero decides to stay with heroine. Years later they ended up married with children. Heroine's daughter rude to heroine repeatedly. The hero seems to regret giving up everything for the heroine. He decides to leave and they separate. Heroine later meets a gym teacher who flirts with her. The hero and heroine later reconcile. I don't know the name of this book and can only remember part of the plot. If anyone knows the name please let me know. I would appreciate it