Have you checked your chain lately? Manufacturers such as Shimano recommend replacing your chain once the wear reaches between 0.075 mm to 0.1 mm. Using a chain measuring gauge like this Rohloff Caliper 2 chain gauge, allows for fast and easy inspection.
By pressing the tool into the chain, the amount of wear is measured and displayed. Once wear has reached 0.1mm, it is time to replace it. By knowing the wear, you can maximize shifting quality and chain life.