It will NEVER be the way it was. Trust me.
This man does not love you. You are a place to put his penis, nothing more.
You need to find a way to go cold turkey - rethink your free time, engage yourself fully in activities that don't allow thoughts of him. Spend more time with your daughter, go on a holiday, do some self-CBT, anything!
But please, work very very hard at putting this man behind you. You will NEVER live happily ever after with this man, and carrying on will harm both you and your daughter, no matter how hard you try to shield her from the situation.
The girlfriend, like him, is not your problem. Disengage completely and absolutely with all of them. Do not pass their house, do not answer the phone to them. Change your mobile number. Block them on facebook, and then get someone you trust to change your facebook password so that you cannot go on there for a month or two. Remove any photos you have of this man, or any of his possessions, and throw them into the dustbin on the morning that the bin men come round so you can't change your mind.
You need to be firm, and drastic with yourself. For your sake and the sake of your daughter. You will not be a good role model for her by allowing somebody to treat you like this.