We previously registered our product's artistic design at the U.S. Copyright Office. A competitor has just started to undersell us by using our design. Can we stop them? Can we get our attorneys' fees back?

Thanks for registering your copyright. That enables you to not only stop the competitor in court but also possibly recover your attorney's fees. Under the U.S. Copyright Act, you are entitled to recover both statutory damages and your reasonable attorneys' fees if you have to litigate... but only if you placed a copyright notice on the product before the copying occurred.