I get what sounds like a similar pain on the left hand side of my lower back - it was so bad the other night i couldnt walk either - and i usually get a corresponding pain on the right hand side of my abdomen (that part feels like a pulled muscle). I second a previous posters advice to see the chiropractor - I see one weekly now I'm in the last weeks of pregnancy, it puts me back together.
It's horrible isn't it!? Unfortunately a chiropractor is definitely not in the budget But I actually slept ok last night after having some panadol. I just don't want to rely on them. Glad you found some relief with the chiro though