So idk what I expect from posting this, I'd just like to get it out in a open-minded group.

Right before the holidays my partner (I'm going to call them L) was out of town and had sex with their ex without asking me, and exposed themselves to covid in the process. This made my past month really aweful. For context, we have not started practicing ethical non-monogomy yet because we are young and have a lot to learn and work on before we do so (this was a mutual agreement). Tbh, if L had asked first, I most likely would've told them to have fun dude. Lol

I'm frustrated because the overwhelming narrative in our culture rn is to breakup with the person who cheats on you. The family I told about it when I was upset is biased this way. Only a close sister (who is also very close to my partner) offered a different perspective but I know she doesn't want to lose my partner's friendship so I'm getting advice that's pulling me 2 ways. There are a lot of sides to an argument flooding my brain. I love L and don't want to end our relationship but I'm worried they are going to take advantage. They cheated on an old partner in college and that worries me.

Idk anyway, thanks for reading if you got this far.