I Think I Love My Wife (2007) on Netflix

Plot summary

Eight years into his marriage to Brenda, a teacher, Richard Cooper has settled into a suburban life with two children and a job as an investment banker in Manhattan. The marriage has stalled, and Richard is frustrated, filling his days with fantasies about other women that he never acts on. Nikki Tru, a single friend he has not seen since before he was married, comes to his office to ask for a recommendation letter. He enjoys her company and tells Brenda nothing about the visit. Nikki returns on the following afternoons to talk or have lunch, saying at first that she only wants to be his friend, and the visits draw the attention of his boss and colleagues.