Wtf ... I am confused. So let me resume everything : he sleeps with womans every night, had a "coup de foudre" to one in a party, slept with her, checked her face without her knowing, returned to his place, saw his fiancee's face THAT HE HAD NEVER SEEN BEFORE, then decided to go to her house knowing it's the woman he slept with last night.
.... I kinda don't like this whole set up.