What Causes Numbness In The Legs?

I have SLE and JRA and I have new symptoms I'm trying to make some connections with. My legs feel like they are made of rubber and it feels like I'm walking on the moon. I get burning sensations in my face mostly left side.My left foot goes numb and turns blackish. And I'm not sleeping cause my Fibro is flaring up. I'm worried that these are MS symptomatic.... Or could they relate to other conditions/ syndromes within the Lupus?