answer:If it’s your lower back by your tail bone (coccyx) then you might have an inflammed sacrum (SI joint) or you might have sciatica. I had an inflammed sacrum in December and after a couple of days, the pain got worse and worse (because I have a desk job, so I sit down, thus bothering the sacrum which is a joint inside your pelvis). So I left work one day when I was in tremendous pain and I went to the ER. The ER doc diagnosed it as an inflammed sacrum, and was able to give me shots of steroids (to alleviate the inflammation) and a powerful pain killer to make me feel better. It worked. I stayed in bed for 4 days and iced it as often as possible. I also took Tylenol. I then went to acupuncture the next week, and my acupuncturist did some stuff for that. And it all worked. The key for me was icing and staying out of my desk chair (staying in bed).