My (22M) world fell apart today after finding out my girlfriend (22F) cheated a month ago despite what I thought was a perfect relationship.

So im writing this post sobbing like hell i don't have anyone to share how I'm feeling currently

Let me start with some intro

Me and her have been in a exceptionally healthy relationship since the past 3 years like so healthy that both our family and relatives are aware and support our relationship to such an extent that we are 110% sure about our marriage .

We meet everyday have regular (twice or thrice in a week)physical contact and she has a high libido, we have become so comfortable with each other that we have even talked about involving a third when we both are ready so that she can satisfy her libido, this came under strict rules that we will do all that only when both of us( specially me ) are comfortable with this .

So today we were sitting together and I just joked about seeing her archived whatsapp chats (since she usually keeps the boys who have approached her in the archives and also a few people she met on an app named wakie before meeting me and had a good bond with them ,for those who don't know wakie is an app where you can chat or call with unknown people from around the world for 10 mins and then decide weather you want to continue to be friends with them or not ) also note (she usually tells me about anyone who tries to hit on her or approaches her or unexpectedly send compromised pictures to her so I don't check any of it myself I don't even have the right to do so tho)

So coming back, i told her to show her archived chats jokingly and she showed the people who had texted recently and then i randomly started asking who each person is and what they do .. we are chill about it , and then a person came by the name XYZ and and I asked who is he, she said someone from Punjab and then we moved to the next but I saw what his recent text was something like hey why aren't you picking up that made me a bit suspicious seemed like she called him regularly so I asked if i could open his chats and she all of a sudden became all defensive that no dont open and that increased my suspicion by a lot like why would she try to hide it from me then she snatched her phone from my hand and closed it this just made me loose my mind I started asking her repeatedly to show what's in his chat and eventually she agreed we opened his chat and I read the last 3 messages something like don't call now I'm busy my bf is in call etc and then i scrolled up and saw a message dated a few weeks ago by my gf something like "I told him I'm going to the gym" and then she snatched the phone again and said bs itna hi dekho( that's all you can see) and started acting very weirdly.

I asked her again and again to show me what was written and explain what she wrote but she started saying that i should not check her phone like this since she also doesn't check mine and that i can't read her chats like this it's her privacy i just couldn't understand why did she start being all defensive and refusing to show me what it was .After asking her what it was for more than 10 mins she showed it to me.

The situation was she wrote those words telling him about how she lied to me by saying that she was going to the gym and went with a 32 yr old person she met on insta to a remote area in his car and got physically involved with him that day ) and seeing that I just broke down, completely blank, i didn't know what to do ,I was feeling so helpless .I couldn't even cry ,my heart was just screaming inside. Everyone around knows about our relationship and that we were a perfect couple and some felt jealous of us .

From that situation we finished the class we were attending and then she dropped me home( we both have our personal car which we alternate )in complete silence not even a sorry ..like it was justified.. she said it was only s*x she didn't love him or anything

What the fcuk am I supposed to do if that was just s*x I felt so betrayed !!

Now I can't share this with any of my friends or family because everyone knows her personally I didn't want to ruin her image in front them so now I'm here writing it all up with my t shirt wet from my tears ,

Can anyone help me, what should I do this situation (please don't hate on her ) I want a mature answer considering everything I've said i cant just breakup with her.

And also tell me if i should separate the physical contact from emotional because from what she says it was just a one time thing with the other person and she is mine and only loves me for life.