What Causes Severe Pain In Lower Spine,knees And Hips?

Hello.I am in very severe pain in my lower spine, knee, hips and sometime times costochondral area. The pain has become unbearable....preventing normal exercise that a used to do. A Rheumatologist diagnosed AS about 9-10 years ago and her diagnosis was disputed by a second doctor. Now that I have a Neurostimulator I,planted in my spine, it isn t helping and I m very overwhelmed.