rsk, I am going to share an email that a very good girl friend of mine wrote to me when I needed some wisdom. It is one of my treasured emails because it reminded me to be clear-headed when I really needed it. This email helped me so much... I think it may help you as well. Besides removing my real name on the email... the rest is left unchanged.
Hi ____,
Sorry it took so long to get back to you.
My first reaction is to say "to hell with him." The odds point to him not having changed one bit. If he is still calling you and saying nice things to you, but then has a girlfriend, then this would indicate that his behavior is the same old behavior that it has always been. I would imagine that his new girlfriend would not approve.
I would also remember that being in a relationship does not equal happiness. There are many people who jump from relationship to relationship, in an attempt to fill some void in their life. It does not create happiness, but causes misery. It is often a kind of addiction in itself. I vaguely recall something about how addicts should not be embarking on new relationships early in their sobriety, as this jeopardizes sobriety. My guess is that this woman is in for the same hell ride you had, and that sucks for her.
Let us assume for a minute, though, that he has changed, or that this new woman is giving him the stability he needs to change. In which case, he has taken a lesson from you and turned over a new leaf. If that were the case (I doubt it is), then the compassionate approach would be to be happy that he has made the changes you wished he would make.
Either way, it makes no difference. You are focusing on the wrong thing. It is not that you could not give him what he needed to be happy. Addicts are, by definition, miserable. He was an addict before you, and was one after you. His inability to change, or to seek real happiness, had nothing to do with any shortcoming on your part.
What you should remember was what you had to go through. HE made your life miserable for three years, and that was very much because of shortcomings on HIS PART. You could not change him. That is not your fault. You are now out of the relationship. You have moved forward. The best case scenario is that he finally learned and will do better in the future. I doubt it. BEsides, even if he has completely changed, you could not function in that relationship, because of the past.
The best thing to do right now (I know this is hard) is to avoid all contact and not look at facebook. Even after months apart, he still has the power to jeopardize your future. That, in itself, should let you know why it is a blessing that you are out of that relationship; why that relationship would never have worked; and why, no matter what he is doing in his life now, he cannot be a part of your life in any way.
That's my two cents. Hope it helps. Keep strong, and move forward.