What Causes Abdominal And Back Numbness?

Hi.... I've had abdominal and back numbness on the left side since november of 2010. It is constant and there is no tingling sensations. I've gone to the doctor and have an appt with a neurologist in october. I'm 33, female... and 200 lbs. I was diagnosed with bipolar in 2003 and since then have had various fainting spells... the last one causing me to fall on my back.