How to cut wood with chainsaw?

When I buck wood with my saw, the saw weight should pull the bar and chain through the wood, right? For some reason, its not cutting that way. Its only cutting when I do the opposite, push the saw up, forcing the end of the bar through the wood. I tried to sharpen my chain and file down the depth gauges to the right height, but its still not cutting right. Am I doing something wrong? Thanks!!