Yes, stop doing the scorpion! You are either doing it incorrectly or you are injured. Ask your coach to look carefully at your technique. If your technique is good-assuming your coach know's what she/he is doing-then the problem may be medical. Pay close attention to this problem and get it fixed now before you hurt yourself beyond repair.
Well so far from reading your post.
I believe the best thing to do before doing your scorpion
is to stretch your back out and warm up your body to prepare it for moving in that motion. Make sure you do this everytime.
I also prescribe that you purchase a heat pack for your back at your local CVS or pharmacy, and apply it on your back when you go to sleep or when you have some down time.
See how this helps in a few days, if the pain gets worst or persist. Visit your Doctor or chiropractor.