Elain, Using a marble, hopefully you don't have carpet, determine which way the floor is sloping throughout your home. Map the direction and slope intensity using arrows over a floor plan of your home. Include you existing pier placement in the diagram. Once you get an good idea of which piers are failing and where your settling is occuring you can go about remedying the problem. In many cases, homes setting around the perimeter walls, creating a v-shape. In other cases, the home may settle inward, creating a u-shape.
Concrete pads, hydralic jacks, cinder blocks and cedar shims are the next step if you're planning on doing this yourself, which it sounds like. It's a hard and potentially dangerous job, but if you're carefull and do the job over an extended period of time you'll do fine and save alot of cash. A contractor will have to replace piers to your city's code, which often carries a price of about $200 per pier.