What Could Severe Pain In Back, Nausea And Headache Indicate?

I have had back pain and headaches for 3 weeks. Went hospital they did cat scan of head and blood work. Nothing wrong. Still had back pain went to doctor she said i could have pulled something to go to chyropather. Then said I had inflammation on spine. Today lower back pop started to have severe pain in lower back sudden nausea and no have a really bad headache. I can walk but it hurts to walk sit up or even do anything.