There's a big difference between running your knife along a sharpening stone and actually sharpening it. Here's how much pressure a Master Bladesmith recommends you need when you're sharpening a knife with a whetstone. Photo by Didriks.
According to Bob Kramer, certified Master Bladesmith, the lack of adequate applied pressure is one of the most common mistakes when sharpening knives. Kramer suggests you use two to three kilograms of pressure for a relatively in-shape knife, and around four kilograms of pressure for a really dull blade. If you're not sure what that feels like, press down on a scale until it reads the correct weight, and apply the same pressure to your knife when you sharpen it. When in doubt, apply more pressure than you think you need. You can find more great knife sharpening tips at the link below.