My ABS light (Explorer) has been on for three years. It doesn't mean the brakes have a problem, it's just the ABS itself is not functional. I prefer straight disk brakes so I never had it fixed.

You have an ABS sensor on your driver's side rear brake. The sensor could have come loose, and the pads you had put on in January may not have been seated properly.

In any case, STOP DRIVING! Get the brakes checked right away!!

YOU ARE A DANGER TO YOURSELF AND OTHERS!