It sounds like you may have sciatica with the "shock pain" you're describing in your buttocks. If you have been moving as Pa Lady suggests, that certainly could have brought that on. I am speaking of personal experience here lol.
Do call your doctor's office and ask to have your appointment moved up. Describe to them your symptoms and tell of the pain you are feeling as well. You should be seen as soon as possible.
Break out the TENS unit, if you have one. If you don't, then ask about getting one. Use moist heat as well on your lower back and keep your knees gatched when you are lying down (keep them bent at the knees with a pillow or folded blanket underneath.) Bengay helps some people (it does help me) or some other arthralgic over the counter rub to bring heat to the lower back and buttocks. Warm baths may or may not help as well.
Hope this helps. Will include you in my prayers.
Moderator Chronic Pain
Believe in yourself. Be kind to fellow humans and animals. Take time to smell the flowers and the coffee.
And by all means, when you are down, ask me for help. I will be there.