Extreme bone/nerve pain in coccyx without injury, weakness in legs, unexplained weight loss, loss of appetite/digestion problems, lethargy/fatigue.

See your PCP ASAP! Too little info to go on,Many unanswered questions here? Given the variety of symptoms paired with loss of appetite, lethargy and weakness an urgent visit to your primary care doc is definitely in order. A detailed history & Physical exam including weight loss h/o over a certain period of time, labs, and possibly an MRI if deemed necessary by physical exam would not be out of the question.