Stress Fracture in Femur not healing accompaned by cramping at

I had a stress fracture in my femur the end of July 2011. The same leg I had a hip replacement done 4 years ago. The repair was a metal plate, cadaver bone and lots of wiring. Four months in and the cadaver bone broke!!Bone is not healed yet. I started using a bone stimulator on it and now I am having horrible cramps in and around the surgery site and feels like right into the bone!!! What is this??? Any ideas. Just want to know if I am doing something wrong?? Thanks