Emma starts sleeping around and isn't very subtle about it

It becomes clear to you over the course of the next week that Emma didn't end her cheating on you with Mason. First it's just that Emma's is out more and comes home looking disheveled, but once she starts bringing guys home to your apartment when you're not around you can't pretend you don't know what's going on, because when you sniff the bed and the used tissues in the bathroom wastebasket you can smell the distinctive aroma of cum.

The bed is where it's most obvious - day by day your duvet gets messier and messier from what seems like constant fucking. Sure, you're having sex with Emma almost everyday, but when you come home and sit on the bed and find it's still wet - you know that's not from you. It's not just crusty either - but there's visible cum stains.

And yes, one day you came home while Emma was in the shower and you looked down at the bed you found a fresh puddle of cum. You must have just missed her in the act with someone by minutes.