Blown Fuse

I just replace a new brake light switch, bulbs, fuse and brake light connectors. Soon as I pressed the brakes they blow the fuses right away. It also did the same thing with the old brake light switch before I replaced it. The fuse amp for the brake light is 15A, but I have two fuse boxes in the rear seat of my Cadillac on both sides. Only one shows the fuse 15A for the BAS on the left fuse box, but the right fuse box does not have it. I need to know how to get my brake light working again and what causing the fuse to blow soon I press the brake pedal. Also, there is a black amplifier box on the left in the trunk connect to the circuit and on the right side is a small silver box connected to the circuit.