Have you done anything that would make her want to cheat? Are you and her still intimate when she is home?Until you have proof that she is cheating ,it would be a bad idea to confront her about it until you do.I always have felt that most affairs or cases of infidekity start or originate at the work place. Your solution will take time and patience, good luck

You can bluff her ;)

Tell her you got an anonymous sms or something telling the author saw them very intimate in the company or something like this. Depending on your acting you maybe you get her telling you the truth.

Just fuck the shit out of her dude ,that what she wants

Cheating or not cheating.. in both the cases you can't do anything.. if cheating than what's the reason focus on it instead of finding out the cheater in her... if not cheating then inspect yourself why you are becoming more possesive... most important thing is that many of the time you distrust and doubts, actually start working and nonetheless your partner being devoted to you some time take out the hidden feeling of change.. change is inevitable.. either you give her new things.. enjoyment.. life style.. memories etc.. or she'll find it in her own way.. it doesn't mean girls only go for other man.. then could be inclined to anything.. their career.. some passion.. back biting and most of the time slow depression... if you want to come out from this think of the extreme loss... cheating is not a proper word.. need for other things is the right way to think.. if she is in need of change.. even if started working hard in her career you must focus on your part an not her timing and relations.. osho said once... no body can eat same vegetable everyday.. in marriage and relation you cannot change the name of the relation but you can play differently to keep it alive and new...