Seeing Other People (2004)

Directed by Wallace Wolodarsky

Ed and Alice are two months shy of getting married when she realizes that she wishes she'd had a more active love life while still single. Reluctantly, Ed agrees to have an open relationship in the months before their wedding, and initially this seems to improve their connection, particularly in the bedroom. However, as Ed and Alice get more involved in their own flings, the experiment goes awry.