Brakes sticking in rear just changed pads and

The calipers might need to change also.

You need to make sure the caliper pieces slide freely on the pins and the piston also moves freely. I just did my daughters GM car. I had to pull back the rubber boots, thoroughly clean the pins and relubricate them with the correct lubricant. Worst case scenario, you may have to replace the caliper pins or get rebuilt calipers.