How to Tell if Someone is Cheating on You

Maybe your partner had a sudden spark of inspiration and realized it was time to get real and start hitting the gym. But it could also mean your S.O. has someone to impress who isn't you.

If she's gone from baggy tees, yoga capris and flip-flops — to which you've become accustomed over the years — to sexier tops, figure-hugging dresses and shoes cobbled by an actual designer, it might be that she's trying to catch the eye of someone who isn't used to her lounge-around-the-house outfits.

It may not signal the end. Check out these celebrities who survived cheating and stayed together.

It's one thing to actually protect your phone for security reasons, or ensure that no one eats up your five precious Candy Crush lives, but if he or she suddenly starts doing it when they previously didn't care and refuses to let you in on the password, beware.

Granted, if he just came from the gym or played some sweat-heavy sport, by all means, shower away. But it's when he is "stuck at work" for 14 hours after a long day of meetings that went into the night and doesn't want you to smell the alcohol on his breath and the perfumey scent that isn't yours wafting from his shirt — then that's a problem.

Need more info on the signs you should watch out for? Don't miss 10 secrets your cheating spouse is keeping from you.

Sure, musical tastes can change as we grow and evolve, but when she suddenly develops a passion for jazz and doesn't share it with you, that's a sign that her new love for Miles Davis may be influenced by someone new.

Learn how to spot more red flags with our list of the top 10 reasons why marriages fail.

Well, duh. Discovering he's cheating with a friend? That's when things can get really ugly, like these 22 messy celebrity breakups that go down in history.

If he was a former missionary man and is keen on trying different things, watch out. Yes, he might have been reading a book on "101 ways to please your wife," but he also might have picked up a few tricks from his new mistress that he wants to sample on you. When his sexy time interests start to vary, it could very well be because things are heating up somewhere else.

Were you previously experiencing any loss of intimacy? See the top 10 reasons why people fall out of love.

If you notice a significant chunk of money missing from your joint account, or there's a new bank app on the computer that isn't from the branch you know your partner uses, and you ask about it and they change the subject? Question that.