I have a very similar story, my boyfriend who I lived with broke up with me last week and I'm devastated. I found out that not only did he start seeing and sleeping with a girl in the week before we broke up he is now seeing her and saying all the things to her that he once said to me. This girl was not unknown to me but whenever I questioned their friendship he made out that I was jealous and possessive and unfair. I loved him with all my heart. He has cut me off completely and doesn't want contact. He left and moved on and left me to drowned in despair without showing any compassion or care. Like you I cannot express the range of emotions I am going through, I just know it hurts.

I did write something this morning as I just need a release.

It's meant to be hopeful and it's where I want to get to emotionally but not sure I'm there yet;

If you can accept the bad things that have happened you can begin to walk away,
If you can reclaim those parts of you surrendered to others you can begin to be whole,
If you can forgive the lies and betrayal without betraying yourself and becoming bitter,
If you can bare the gripping twisting of your heart and know that although it's in pieces it continues to beat,
If you can mourn the person they were and not blame them for the stranger they have become,
And when treated with contempt not give in to holding them so

If you can look at the clouds and still see the wonder,
If you can resign yourself to a new unknown and not turn away from the fear that it brings,
If you can smile at the memories and not let them blanket the future,
And think about those who made you cry but appreciate the smiles they once brought,
You are bird learning to fly into the wind