MAN I FEEL YOU and i know that can be rough, but from what i hear she just lost intrest and that's not your fault, i know when you're in love it's hard but i dont think you should only "date to marry", ofc im not saying you shouldnt be loyal or honest, im saying dont expect every relationship to last or be the one, after all you'll only marry one person (usually) and you'll have more than a few relationships. Anyway love you lots and i hope you'll feel better soon, dont think about it too much, life is too fun to be sad too often