The Age of Innocence
The story takes place in New York in the 1870's and involves a romantic triangle between a socialite (Winona), her cousin and a guy. The guy is engaged to Winona who plays a sort of quiet socialite person, while her sister is passionate and a little wild and has been involved in scandals.
A guy named Newland is engaged to May (played by Winona Ryder), but her cousin returns to New York suddenly he see's a chance at something a little wild.
There's also some narration. The film is also centered on the ultra-rich, gossip and what was perceived as "proper" behavior (even people didn't generally follow that. )
Newland is playing around with the blond countess even while he's engaged to May and starts again after he and May get married.
One of the reasons the movie is boring, in my opinion, is that you can see what is going to happen way before it does. Everything is too obvious. Ryder seems to be playing a very dumbed-down role, much unlike the normal roles that she plays.
You should realize things are bad in your marriage when your spouse says he (or she) needs to take some time off by himself/herself and maybe go to Japan for a while. May's answer is that he can't leave without her because she's now pregnant.
So, time goes on, she dies, blah, blah, blah.