Be patient. I started passing stones at 7am the morning after my first flush and kept passing them until after 9pm that night. It's early still. You could still have a big day ahead of you.
Post later and let us know if you've seen anything. Don't get too discouraged. IF you don't get any stones you are certainly not alone. Stick with the program. I'm about to do my fourth and I really think it's worth the effort.