Please don't beat yourself up any longer. People who go for WLS have come to the end of their rope with wonder diets, miracle cures, slimming pills, self-hypnosis CDs, etc.
You have opted for surgery because you feel that you just cannot lose weight without help. For very overweight people - that definition once included me - losing weight is the hardest thing in the world. This is why so many turn to surgery. Who in their right mind would even consider an operation, if they did not believe that they would never ever be able to move forward, without it?
Of course you are finding it terribly hard to lose weight, particularly as the waiting-time drags on and on. You opted for surgery BECAUSE you need help to lose weight. Making the decision to go under the knife does not magically bestow upon you superhuman dieting powers! You are still the same person, with the same difficulties. You are one of countless thousands of people - millions, perhaps, the world over - who have a problem with food, weight and body image.
If I could give one piece of dietary advice, it would be this. Cut out sugar and white flour. Watch your carb intake like a hawk. You'll be advised to restrict carbs after surgery, anyway, and will probably need to keep carb intake low for the rest of your life.
Most overweight people are addicted to carbohydrates - sugars, starches. Sweet things, savoury things. Sugar, which is absorbed into the bloodstream superfast, triggers cravings and binge-eating. You have nothing to lose by experimenting for a few days - preferably a week. Cut sugar out completely, try not to eat pasta or rice or bread. Instead enjoy lean meat, chicken, pork, fish and seafood with plenty of green or low carb veggies on the side. You may be amazed by the results in terms of appetite reduction.
Good luck in whatever you decide x