I hate myself for what I did

I shared my story

http://www.lisaescott.com/forum/2013/06/28/he-really-narcissistor-am-i-j...

on this website some time ago and the replies have been really helpful. I've been doing quite ok with NC until last week when his birthday came. I couldn't resist the temptation and looked up his website and Twitter. In one of the comments I saw the OW's friend wishing them all the best. I was devastated as he told me the OW (he cheated on me with her) was nothing, that he did not care about her and that he told her it was over when he wanted to make amends with me.
Seeing that they are officially dating now I was so upset that I wrote him an email where I wished him a happy birthday and told him I missed him so much. He replied that he missed me and loved me too a lot but did not deny dating the OW. I then decided to check whether he still had feelings for me. I told him that I am willing to move back to China to make it work again (not true, I was just hoping he'd jump at a chance to be with me together and dump the OW). I thought if he said yes it would make me feel better about myself. But the reply came and he told me it was better to move on. A guy who was begging me to give him another chance just 2 months ago, a guy who assured me of his endless love for me said NO to an opportunity to be with "the love of his life" again. It hurt me so much, is he that happy with the OW now that he doesn't care about me at all??
I hate myself for trying to prove my worth this way and getting the opposite result. I feel like some trash, someone, that can be just stepped over without even looking back...The recovery has been so hard and my therapist has diagnosed me with depression even before I did that stupid thing, now I feel like I don't have anything left, not even remainders of my self-esteem to keep me going...