Low Back Pain Came On Me Yesterday Morning Over About

Low back pain came on me yesterday morning over about an hours time, no strain or movement involved. Some lower GI distress also. Felt like constipation but was able to have bowel movement with no pain. I had low back pain all day yesterday and most of the night, bad enough to keep me up. I thought it might have been appendicitis but pain diminished by this morning. I noticed my urine was unusually dark today. Not much pain today but pain is now starting to return.