I have heard the Chinese Bitters from Sensible Health do a great job of breaking up stones. I plan on trying it with my next flush. I would recommend trying a different recipe also. I have a hard time with the thought of using coke to achieve good health. Seems like a bit of an oxymoron to me. If you mix grapefruit juice with the olive oil, it tastes tons better than lemon. Also, you could use a lighter tasting oil like walnut. I have used it with great results. It what you are trying isn't working, then feel free to switch it up a little bit. Also think about bowel cleansing too. You might be releasing stones, but if they don't have a clear passage out, they will just sit in your bowels.
Good luck. Don't give up just yet.