Tell me please which sentence sounds the most natural?
I injured my back so bad, that at one time I couldn't even walk.
I injured my back so bad that at some point I couldn't even walk.
I injured my back so bad that one time I couldn't even walk.
What I am trying to communicate is that on one occasion my back was so bad that I couldn't walk. If none of my sentences sounds natural, what would a native English speaker say?