Being cheated on is one of the most devastating things that can happen in a relationship. It can be especially jarring and confusing when you find out that you were actually the person being cheated WITH, making you the "other person" in someone's relationship.

Perhaps your boyfriend was in the shower when you noticed his phone blowing up with notifications. You normally never touched his phone, but you decided to peek in case it was an emergency. You saw tons of Facebook notifications, though he told you he didn't have a profile. The notifications were dozens of comments and messages congratulating him on his engagement. You confronted him when he got out of the shower, and that's when you learned he had proposed to his long-distance, longterm girlfriend over the weekend, and you were just his secret sidepiece.

Maybe you began discreetly hooking up with a fellow regular at your local bar. One day, you were at the bar chatting with the bartender and let it slip that you'd been sleeping with this woman and were starting to catch feelings. The bartender's face dropped, and he told you that the woman you were hooking up with was married and her husband was deployed overseas. You were devastated and told the woman to stay away from you and the bar, or you'd tell people about her infidelity.

Or, maybe you began chatting with someone on Tinder and made plans to meet up. Before your date, you and your bestie used the minimal info from their profile to do some internet sleuthing, and you found them on Instagram. Turns out, they were in a longterm relationship with their high school sweetheart. You DMed their partner screenshots of their Tinder profile and your messages about meeting up, then blocked them both and deleted your Tinder account.

Have you ever been the "other person" in a relationship? How did you find out? Tell us your story in the comments or submit anonymously using this form for a chance to be featured in a BuzzFeed Community post.