This is basically a "slipped disc". The squashy yet firm "disc" in between the bones in your spine which act as buffers, can wear out, or suddenly be squeezed due to bad posture, heavy lifting, being overweight etc. Once they are out, it's like toothpaste out of tube. If yours are just bulging, that means they are under stress but you can help this by losing weight, doing back strengthening exercises, lifting and bending properly etc. Chances are you have some lower back pain, which means the discs are pressing on the nerve in your back (sciatic) which is the long one that runs down to your feet. This is why some people get leg pain with a back problem. Get a book on back care and try and strenghten yours up.