I (26F) have been experiencing grief over a potential breakup with my boyfriend (29M), even though it hasn't occurred yet.

I (26F) feel like I'm already grieving a breakup that seems inevitable after nearly 10 years together. My boyfriend (29M) and I started our relationship when we were just 16 and 20 years old. The first couple of years were challenging, particularly due to a few incidents of infidelity on his part. However, we managed to work through those issues with open communication and honesty, and nothing of that nature has happened since. We experienced a strong connection, embodying the "opposites attract" cliché, and for about five years, our relationship flourished. Sadly, over the last three years, it has begun to fade. During my teenage years, I faced many struggles and felt an intense need for his love. Issues with my parents led me to consider emancipation at 16, and I eventually moved out at 17 to live with my boyfriend and his family. My relationship with my parents has improved significantly since then, and we've built a wonderful bond. However, I'm concerned about how a potential breakup could affect our current dynamics, especially since my boyfriend wishes to stay connected to my family, which I cannot control—and wouldn't want to. I'm also close to his family, and it's heartbreaking to think I might lose that connection. My boyfriend has been there for me during both the highs and lows of my life, just as I've been for him. We have three wonderful cats together that I couldn’t take with me if I moved out. Returning to my parents isn't an option for me right now, and I’m in the process of improving my financial situation so I can eventually live independently. The only feasible housing arrangement would be with my best friend, her fiancé, and her two lovely daughters (ages 6 and 8), whom I consider my nieces. However, I worry that my sadness might strain our friendship if I move in with them. For the past few years, my boyfriend and I have felt increasingly out of sync, primarily due to differing political views, philosophical beliefs, and attitudes toward money and value. In our decade together, we’ve never taken a break because I believe in an "all or nothing" approach to relationships, and I’m not convinced breaks would be beneficial for me. Tonight, we had an extended conversation about how our differences are driving us apart instead of bringing us together. We both feel that our life together has become mundane, with more bad days punctuated by a few good moments. We want the best for each other and acknowledge that we deserve to pursue true happiness—yet we’re uncertain if that can be found together anymore. I feel like I've been hesitant to confront this for the last couple of years, though a part of me has been ready to move on. My identity feels intertwined with him, and I'm scared of who I might be without him. I’m feeling lost and anxious about what the future holds, whether we should make an effort to stay together longer or officially end things and seek our individual paths to happiness. Thank you for taking the time to read my lengthy, but only partially explored, post. How do we choose which direction to take? What coping strategies could help if we do break up? How can we have a constructive discussion to reach a decision? I would love to hear your thoughts. TL;DR: My boyfriend and I have been together for about 10 years, and we’re contemplating a breakup. I find myself mourning the loss of our relationship before it’s even ended, and I’m unsure about what steps to take next.