Eventually, you've got to let go of your ex-girlfriend so that you can move on to bigger and better things. Here are some steps to get you going.
1. Call your old friends up and ask what they are doing so you could hang out and do guy things.
2. Start a hobby and get really good at it.
3. Take down all her pictures and anything that reminds you of her.
4. Move your furniture around, buy fresh new bedding and paint a wall a new colour to reclaim your space as your space
5. Round up all the ex's belongings in your home and put them somewhere in a bag/box. Just keep them out of sight. Don't worry about getting it to her, you'll only make it an excuse to see her otherwise,
6. It might seem impossible at first, but try flirting with other girls, even if you don't like them. Eventually you'll find one you like.
7. Work out, it may help the pain go away.