You admit that this is the third time your partner has broken up with you. I know it hurts and sucks, but it’s time to move on. You shouldn’t have to convince someone to love you and be with you. You deserve to be with someone who wants to be with you and your (now ex) partner has the right to walk away amicably without being assailed for it (even if it would make you feel better emotionally for a time).
I’m sorry you’re having this experience though. I’ve been there and it’s the kind of thing that sticks with you. But you can and will get past it.