sounds like you need to replace your caliper. remove the wheel, hammer out the spring clips that hold it in place, disconnect the flex line, pry caliper off rotor, install new caliper, once everything is back together get some one to push on the brake pedal while you open the bleed screw to release the air out of the new caliper, only open the screw when the brake pedal is being pushed down otherwise it will draw air back into the line, put the wheel on and you're done.