ex boyfriend lost feelings for me

hey ladies I really need your help! so my now ex boyfriend has moved on in the space of 3 days which is the period I stopped all contact with him (yes ink 3 I'm weak.) in this time he slept with the girl he kissed the night before I finished our relationship for kissing her. now a week or so on they're seeing each other, he spends a lot of time with her, sleeps at her house over night etc. obviously that's broken my heart and he says it's because he's lost feelings for me. I asked him why and although he hasn't really explained he's said its because he's feeling the guilt of cheating on me during our relationship (multiple times) and its come to a point where he can't be with me anymore. I'm wondering if there's any way to get him to feel the same again? he says he he loves me and he doesn't want me to move on but he has and he doesn't feel the same? what do I do????? I miss him and it's broken my heart