Don't tell her you're fucking other chicks, she'll know you're saying so to make her jealous and she won't respect you for it. HamHock was totally right when he told you to let this be the catalyst for making your life better. Nothing will make her realize what she's missing more than seeing you rise above this.
You will hurt for a long time, no matter how many chicks you take home to bang in your shower. If they distract you, then greart - whatever helps keep you from wallowing in sadness. I strongly suggest you don't jump straight into another relationshiop however, because you'll just fuck your head up even more. Guys have a tendency to do that after a breakup, I don't know why but many men find it impossible to be alone. Stick close to your friends, go out with them, tell them how you feel, get it out even if you're repeating the same things over and over.
One day you will be going to bed after a long day, and realize you haven't thought about her once. One day you'll think about her and realize it's been a week since you thought about your breakup. After months of good days, you'll have one out of nowhere that wallops you in the heart like a big iron spike and you'l cry like you did the first day. This is just the way it goes. But I promise you, you will get over this.