Looks like it is, at some level, physically-reated, ABM. Slipped disc + some nerve compression. It happens when lifting too heavy weights. Did you experience any sciatica at the time? Though, I have no doubt it is worsened by WD (muscle tightness, poor blood circulation, muscle weakened by WD). Here are some ideas of what you can do:
Post 16 in this thread and the links there: http://antidepressantwithdrawal.info...light=fountain
Very very important - when lifting any weights, do it as they advise in the pictures. If you bend your back (so called "cat's back"), you put tremendous pressure on your spine. Changing this alone (and remembering about it *ever time* you lift weights) can make a huge difference.