Let Him Go!
The fact that he asked someone else to marry him means you are not the one for him. If you were, he would have moved heaven and earth to be with you. He's being engaged to someone else and still wanting to be with you is a big red flag.
Don't you see it waving in your face? He has no concept of what real love is and he is spineless. Let Him Go!
I promise you, when you do, you will find the person who is meant for you. A wise man by the name of Bishop Jakes wrote a poem on this very subject. I don't remember the entire thing but I do remember this line. "When someone walks away from you, baby, let them go!" Don't try to hold on to anyone of anything that is not meant for you. If you succeed in reclaiming it, it will never be the same.