[69-cutlass-S]

Did you install a new stereo or something else lately? It sounds like you have a problem with your wiring somewhere in the car. If you have a good positive battery cable and a good negative battery cable, then you have a wire somewhere else in the car that is grounding to the chassis and draining your battery. I recommend you check for amperage draw at the battery. While you hold the tester leads on the battery posts and read the amperage, have someone pull fuses one at a time until the amperage draw stops. That will isolate the circuit with the wiring problem.