Brake Problem

Well I have been driving around for quite a while with bare brake pads on the rear wheels
andd the other night i was driving and i heard a big bang noise from the rear end and my
rear wheels locked up and stopped the car. I would try and move forward and my rear wheels
would be stuck locked up. The only way i could unlock them is if i reversed and then went
forward again without hitting the brakes. It would do this randomly throughout the night
even when i did not hit the brakes. But the next morning it was fine but now i can press my
brake pedal all the way to the floor and all it does it brake my front tires when it gets right to
the floor. but my e-brake still kinda half works but it is super loose??
Any ideea of what happened? Any help wouldd be greatly appreciated.

Sounds kinda like the pistons on the calipers are locking up when they heat up and expand. Id take those babies out for a rebuild or get some new ones stat.

sounds to me like the brake pad got too thin and flew out of the brake torque member(that being your loud clunk noise), and now youve got some piston on brake rotor action. metal to metal action on the rears causing your lock-up. time for new rear calipers, rotors, etc etc!!

Haha I probably should of taken the easy way and just changed out the pads buut i didnt
want to pay for a shop to do it and its been to cold out lately.
I guess being cold for a while would of ben the best way to do it.
Im guessing this will cost me around 500 or more. Correct or no?