If you’re heart’s not in the relationship, then it’s probably best you leave rather than stay for fear of never finding anyone “better” or more suited to you. In the long term, being in a relationship where he is the one that loves more is probably going to hurt your partner more than the relationship ending. It’s been said many times that until we can learn to be happy with ourselves – and this includes giving ourselves ample time to mourn previous relationships – then we will never be happy with anyone else.