Don't usually post in off topic, but feel compelled to having read how you're feeling.
Mate, I know it won't feel true when people tell you, because your pain is personal to you and what you had was special to you, but trust me when I tell you it has happened to lots of us and time will heal it.
I've felt the pain, the crushed feeling when she seems to get over it so easily, the not wanting to bother with other girls because they aren't her. But like I said, it does go and you'll look back on it as just a stop on your journey.
I've been married for 5 years and have 2 twin 3 year old girls. Every magical moment I spend with them has allowed me to forget any regrets I ever had, as every decision (good and bad) that I made and every moment (good and bad) led me to this point.
While unbelievably painful and crushing at the moment, when you find happiness in the future you'll look back on this period of a painful time that helped get you there.
Don't throw in the towel bud, just get through each day and it will get easier and easier. It might take time but new opportunities will come up.