Throwaway for privacy. Me (F26) and my fiancée (M27) have been in a relationship for 4 years, and engaged for 1. I’ve always felt like our relationship was solid and stable, since we rarely got into fights, and even those would be light discussions. He’s the sweetest, most supportive partner I’ve had, and truthfully I’ve been imagining our wedding for some months now.

Everything came down once he told my mother in law that he proposed to me. I was in the same room, and I could see how her face fell. She pulled him into another room and I couldn’t hear what they said, but I saw my fiancée’s face as if he had been screamed at. My MIL soon after apologized and excused herself out of our apartment, after I asked him what happened he didn’t really answered me, just said that it was “mom and son stuff”. I didn’t pressure on it, but it left a very bad taste in my mouth.

Normally, I told my best friend (F26) about what happened, and she immediately changed the topic. Not really acknowledging how weird it was or how I felt at his excuse. I didn’t really get to ask why she was acting this way, since she always dismissed it or told me it wasn’t that serious and I should be focused on the wedding.

Days after, I met with my wedding coordinator to choose the overall aesthetic I wanted. My fiancée didn’t come with me since he was working, so my sister in law agreed to help me out. I saw this as an opportunity to make connection with his family. SIL was acting weird, almost uncomfortable by the planning. I thought it was normal, and she was probably overwhelmed by the planning.

As I was looking for ideas, my SIL pulls me to the side and says that “she can’t hold this secret any longer, because it wasn’t fair for me”. She told me that her brother and my best friend had been seeing each other behind my back, and my MIL found out about this, but told her he would soon break up with me. I was gobsmacked, I asked if she was sure of this and she said it’s what she’s heard, so not 100% sure.

I confronted him about this, and he only responded with getting mad at his sister and me for believing “gossip”. I tried to understand, but as the days went on I couldn’t handle the nerves and I left to my cousins’ apartment. This morning, I sent out an email and messages to all my family members, saying that the wedding was cancelled. I really want to confront my best friend, but I know she will deny everything. With the wedding being so close, I couldn’t handle the anxiety I felt.

He has been exploding my phone with messages since I left, and I don’t know what to do.