I also recommend a honing rod; a good ceramic one will run you 40 dollars or so. Takes some skill to use, but it will change your life. Your blades need to be realigned.

It differs from a sharpener in that a sharpener takes material off the knife. You should hone every few weeks; sharpening should come once or twice a year. Sharpening too frequently will a noticeable reduction in the knife's physical size relatively quickly (not that it still wont cut).