Is it unfair to your gf/bf to want to go seperate ways for no particular reason?

I've been dating my gf for 2 years, and I love her a lot, but where at different points in our lives. We knew this going in, but dated anyway. And we've lived together for 2 years now. I feel so guilty because I'm the one who is thinking about seperating and I know it's not for great reasons, and reasons that we already knew and talked about before we started dating. I feel like I would be betraying her since I chose to be with her instead of realizing we were at different points from the start. It's really confusing me and tearing me up and I feel like I could go either way with it. My head is saying were at different points, but it might be too hard for my heart to let go. I dont know what to do but I need to make a choice because everyday the thoughts and feelings battle each other. ugh..