I’m looking for the name of a movie. It’s in English, setting seems to be in the 40s or mid 1900s, but I don’t think that is when it was made. Movie is in color.

The general premise is that a husband is cheating on his wife, and the wife eventually befriends the mistress. The mistress becomes pregnant. The wife fakes a sickness (6 months to live) so the husband will be more loving to her. When the husband finds out that the mistress he decides to be with her (but tells her he needs to wait 6 months for his wife to die).