Justtrae83, sorry you are feeling this way. It does hurt. I know pretty much exactly what you are going through, so vent here! I don't think anyone likes to hear this, I know I didn't, but Time will Heal.
If he's with another in a month, then it's a rebound and won't last. He hasn't changed his habits in a month! He has to have someone take care of him, and that's not you now.
Don't want to "Kill" him, he's doing that on his own. If anything feel sorry/empathy for the new girl that will have to go through what you did.
Hang in there.