Hey Ken, take baby steps. Time heals all wounds. It is going to take time for the feelings to go away. the most important thing you can do is move on. By move on I mean don't hang out with her.
Girls have a strange habit. They feel awkward when people don't like them or are unhappy with them. So, as a result, there are a good number of females who try to maintain "friendships" with ex-boyfriends. Generally speaking it isn't to be malicious but is the way they prove to themselves that their ex is still on good terms with them. Even if you are on "good" terms the best thing to do is stay away. The time away will give your psyche time to process the feelings you have and allow them to subside. As harsh as some of the advice you've received seems, it is true. Go out, have fun, spend some time with your sister. Occupy yourself your time with activites, other than GCCG. Go to a gym, play horseshoes, spend time with other 3D people.
There is nothing you can do about the pain except wait. The only thing that may help subside it is talk about what you're feeling. By talk I mean verbalize (talk don't type) your feelings to a close friend or relative. If you must write something put it down on a sheet of paper. Write out all of your frustrations from words to curses to scribbles to holes in the paper you make with your pen. Once you're done take the piece of paper, rip it to shreds and then burn it. This sounds funny but this method has been proven to be theraputic.
The memories will always be there, and short of amnesia nothing is going to remove the memories. Is this your first girlfriend? If so, you are about to experience some very important personal growth. With that growth you will find new strength which you can embrace and use to move on.
The most important thing you can do right now is stay away from her and verbalize your feelings to a close friend. Good luck, keep your stick on the ice, we're all in this together.