I remember watching it on a New Years Eve on Playboy or Cinemax or HBO or something along those lines.

It was about a photographer who ends up cheating on his wife with one of his models. I remember a scene where he was going down on his wife under the covers and she was not enjoying it, I believe he cheated because his wife did not enjoy sex.

I believe that the model became obsessed along the line. The wife was a pale woman with very large breasts, the model was darker skinned.