how to cope with heart break?

Becky
does anyone know what is like to have someone tell you everyday for a year and half that they love you and need you more than anything in the world. you're their soulmate, other half. promise that they're willing to fight through anything in order to keep you for the rest of their lives.
I always knew in my head that promises like these were pretty much impossible but he said to me over and over "I'll prove it to you, you'll see im never going anywhere I'll always be here to love and support you."
and then one day literally over night, after saying these things the day before, just completely cut you off, say it's over im sick of you without any explanation what so ever.
I honestly don't know what to do with myself at all, I feel like everything I ever believed in has been ripped away and I can't even move, eat or sleep.
has anyone else been through this?
I'm thinking I need a rebound but I feel like that will only make me feel worse in the end.