This is normally due to warped rotors, which can happen for various reason, rather than just warping over time. This is the most likely scenario, but it'd be best to take the car in to a shop and be sure to know why the rotors are warping so soon or to determine if there is another problem. It's a safety issue.
I have a 1996 Honda Accord and I am having a simular problem with my brakes. I recently had the rotors turned but the car is still shaking and and vibrates and makes a loud noise whenever applying the brakes as I come to a stop. What should I do?
Use good quality parts only when it comes to brake pads and rotors. Make sure the wheel bearings are good, it's very important that the surface where the rotors mount to the hub is good and true, if not the rotors will continue to warp.