Please help me...very sensitive, emotional situation?

Wow.. ok he isn't over her and she isn't over him. It was unfair of him to bring you so close when he is still emotionally intimate with someone. He is an emotional cheater and sadly the more you try to push the two of them apart the more he will resent you secretly. If I were you id separate from him until he is ready to fully commit himself to you. I know that sounds scary to do 'cause you love him so much. BUT! Do you think you want to feel the way you feel now for the rest of your life? It's miserable to fell like your second fiddle when you are going to be his wife. Don't sell yourself short. He is not being fair to you. Stand up for your feelings, it's ok. Lastly, try to view it from the outside, it might put things into perspective.