1999 Plymouth Voyager abnormal wearing

I replaced the front brake pads less than a year ago. Back then I noticed that the driver side brake pads were worn a lot more than the passenger side. In fact the passenger side looked fine. I did not think about it too much and changed both passenger and drivers side pads. That was June of last year. The same problem has appeared again. The driver side pads are worn down down considerably more than the passenger side. I drove down the street and tested the brakes really hard and it does not pull to the side. Do you think I should replace my calipers or is something else?