Why does John regret that he had told Elizabeth about his affair with Abigail? What makes her suspicious about John's behaviour?

John regrets having told Elizabeth because she constantly makes him feel guilty for his actions. She refuses to forgive him or try to rebuild their relationship, but instead has a holier-than-thou attitude towards him, making it impossible to John to move forward.

She grows suspicious of his behavior because he leaves out details of his trip to town. John isn't entirely honest with Elizabeth about meeting Abigail, saying that he met her in a crowd not that they talked alone.