Some random suggestions that come to mind:
- If it interferes with work (but you're not ready/able/willing to let go yet), maybe you can try confining playing online to specific and restricted time slots. Make yourself promise that if you haven't snared a hot girl in 15 minutes, then you'll work for another hour. Don't check your messages until the hour is up. Then gradually extend the time you can go without.
- Try to find out what underlying need, if any, your behavior reflects. Feeling guilty about wasting time and hurting your girl is reasonable, but feeling guilty about your own feelings is not productive. Can you think of some other activity that would.. tickle the same spot? Have your gf worship your cock? Something else?
I would also make sure you try and communicate to her that you are concerned about your behavior and that you want to get to the bottom of it rather than push it away (this will make it likely to come back and maybe bite, in my experience!)
Good luck!