Dear readers: Can you suddenly stop loving someone?

From a male reader

When I say suddenly, I mean out of nowhere, just like that, without any reason or explanations everything you've ever felt is gone. I was madly in love with this girl for a year and nine months. In fact I was planning to propose to her on our second year anniversary when all of a sudden I woke up and all my feelings for her was gone. She didn't do or say anything wrong. Nothing about her changed. Nothing about me changed. We didn't even have an argument. One minute we were talking about going on a vacation together and the next minute I stop picking her calls and started avoiding her. It's been four months now since my feelings for her changed and I still can't make sense of it. She wants answers, she wants to know what she did wrong, why I all of a sudden ended things with her. She thinks I met someone else but I didn't. I just stopped loving her and didn't want her anymore. What happened to me? How can I find my way back to her?