brakes stiking

[piking mad]

Hi All. last few weeks when reversing off the drive after being parked up for the night, my brakes aren't releasing, well not without a clunk as thay come unstuck. but they have now got worse my back brakes are sticking just as i came to a stop and have to reverse to free them . any idea's!!!!!!!
1996 3.L SSRX.