Shingles v's back injury

I woke up 2 days ago with a cramp in the middle of my back to the right side of my spine. I tried a heating pad and it didn't work.
I went to the ER and they said I had shingles. There is no redness, no rash, no itching, it's a little sensitve, but I think it's because I have been laying on it so much. not moving a lot.
I know I haven't hurt myself lifting anything, I was find when I went to bed and just woke up in a little pain, took ibuphrophen and used the heating pad.
I am taking the medications for shingles but nothing seems to be getting better this cramp won't go away, it's hurts to the point when I move my head down it takes my breath away.
Could I have simply pulled a muscle and being treated for the wrong thing?
What should I do.