How can I make him realize that I really AM in love with him, and she's not?

first let me say i am sorry you are hurting. it is not right what he did, and it is not really love. i want to tell you this because we fall in love with who we think someone is, and when they show us who they are it hurts so much, we ignore it or say we can move past it. that's okay if you are married to someone, because they obviously loved you enough to marry and commit to you and you should honor your commitment. but you are young and this guy took advantage of you and it is going to hurt for a while. the good part is, you are young and it is only going to hurt somewhat and you will still be able to fall in love with that good guy God has in store for you, you have to follow that. Good wishes.