Sorry breh, I've been there, its like driving for 4000 miles and everything is going smooth and the exit before your destination your car breaks down.
You invest so much, sacrifice in ways you never did, loved like you never did before and it all comes crashing down like pillars on Samson. All you can do now is look at the positives, look at it as a learning experience continue bettering yourself in every area and the emotional ties will get less in due time.
It's going to be tough, your going to feel sorry for her, feel like maybe you should still be a "friend" or whatever but trust me DON'T.
You can't predict the future, you can do everything for a woman be there through thick and thin, have chemistry like snoop and dre on a song but in the end it means nothing. At least you got out without being married or having kids. Breakups especailly after being with someone for years is hard to get over becaue they become so intertwined with your lives.
The switch is what gets most men, we can't fathom how soemone who said they loved us, someone who was there by our side for years, someone who you shared your deepest fears and secrets with, can just switch like a light switch, but trust me it happens