36-year-old man seeks advice to prevent losing his family.

I'm 36, and my partner is also 36; we’ve been together for 11 years. We have two children: a 13-year-old daughter whom I didn't father biologically but have been a dad to for most of her life, and a 4-year-old son that we share. Recently, my partner told me she doesn't want to get married, which honestly hurt. We've faced many challenges over the years, yet we always seemed to rebound. I'll admit that I cheated on her two years into our relationship, something I regret deeply and promised myself would never happen again. Since then, I’ve worked hard to be a supportive partner and father for my family. However, lately, it feels like we’re just going through the motions. The spark we once had seems to have faded, and we're mostly coexisting rather than truly connecting. Things took a turn after a significant argument about her spending habits and a lack of intimacy (it’s been three months). Additionally, I did become close with a co-worker. While it was purely platonic, I confided in her about my relationship, which I now realize was a huge mistake—my partner found out. Since then, she has been acting differently; she takes longer to reply to my messages, goes out with friends more often, and seems distant overall. When we discussed it, she assured me that she still loves me and always will, which I believe. Yet, when I approached the topic of marriage again, she told me she wasn’t interested, which caught me off guard. I recognize that I should've proposed a long time ago, but now I'm left wondering if she's emotionally checked out. I even suspect she might be seeing someone else since she's been staying out late. If she's ready to move on, I can understand—maybe it's karma for my past mistakes. Still, I want to do everything I can to make this work, and I think we owe it to each other to have an open and honest conversation. I'm planning to take her out to dinner soon to discuss everything and understand the future direction of our relationship. I would appreciate any advice on how to approach this without pushing her further away or making matters worse.