Pain in Lumbar-secrum ara radiating to the left

Patient: I am a 24 year old female. I originally developed mild back pain in the year 2008, while I was still a student on teacher training. at the time, I just assumed it was from the constant carrying of heavy bags and books, as well as long hours of sitting in the classroom. the pain came and went and towards the end of 2010, it had become non-stop severe pain.the pain originates in my lumbar-secrum area, radiating to the left around my iliac crest region. i have general weakness in my left foot, with numbness as well as pains and needles under my left foot and toes. i sometimes get cold feelings in part of my left leg and occasional knee lock. any type of physical activities will cause severe weakness in my lower body. going up stairs, running, carrying any weights, sitting for too long, standing for too long cause SEVERE pain in the lumbar-secrum area and weakness in left foot.My CT Scan and MRI shows no abnormalities, except for slight scoliosis. lately, the pain has worsen and i constantly get burning sensations in my lumbar-secrum area. i can literally feel the points on my spine that are in pain.i have done physion therapy on several occasions but to no vail. these pains have affected my work performence. i am tired and frustrated from always having those questions are:1. What could be causing such severe pain and not show up on an MRI?2. Are all the symptoms explained associuated with scoliosis?3. If yes, how can these problems be remedy?the pain never subsides…it ALWAYS hurts. Any information you may have to share would be of HUGE help.