Spells shouldn't be cast to control a person's freedom of will. That's the one thing a person truly owns. Well that's my own opinion on that matter, but your question isn't what to do to control him, it's what can you do to get him back. I honestly don't know what to do, besides confronting him. Not with anger, not with confusion, but with hope. Hope for either getting back together, or releasing your hold on him. Being with him isn't the only way of saying that you love him.
Now about the other women. I don't know much about her or you for that matter, but from what I can tell, love isn't controlling someone, but rather caring deeply for someone. So the statement saying "He is mine." means that she doesn't really love him, but rather lust for him. But that thought is made from what you told me. Ask yourself, really it may sound stupid, but do you love or lust for him? The difference is between the two is both big and small at the same time, so don't rush through with this question.