Adjust your float as was posted earlier, it shold come to the "water line" mark in the back of the tank. Make sure your refill tube doesn't reach down into the overflow tube (it should be above the water), as this can cause a siphon effect.
If adjusting your float doesn't work, you have a leak...not at the wax ring but inside the tank. Put a pencil line at the water mark in the tank and turn the water supply off. Come back in 30 minutes or so and if the water level is below your pencil line you have a leak at the flapper/flush valve (at the center of the tank)...if it is still at the pencil line you have a leak at the refill valve (at the left of the tank). Replace as needed.