Perhaps if you would have kept your social circle, you would not have been dumped in the first place. When you ditch them for your new girlfriend, they will remember that.
The minute you devote your entire life to your girlfriend is the minute you are swimming at sea.
I have ended a few in my life, but usually my girlfriends, after dealing with my bullshit for so long, would finally just end it for me.
For the most part, there are easier ways of dealing with a breakup.
Get yourself back to the gym, buy some new clothes and try and sink into a new hobby for a while.
You will always have the urge to see what her status is or her latest stream of tweets, and you will justify it by saying that you are worried about her. One look at a status update about her recent date or visit from an old friend, and it is meltdown city.
You might have to visit some new bars or hangouts for a while. What you will rationalize is that you are an adult and you can handle it.