What Causes Pain In Back Radiating Down The Left Leg?

I m concerned because I recently had a neuro exam that detected brisk reflexes and clonus. A MRI is not able to be done for a week. I went to the neurologist due to persistant/unrelieved back pain that radiates down my left leg with left foot numbness that has been on going for 3 years. Recently as well have had a 12 lb weight loss over the last 6 months and lab results revealed low HGB. Obv after researching/speak to md I work with (I m a nurse) I have concerns with MS or even worse a lesion on the cervical spine. Should I have any other indicators I should be aware of for either of these illness?