Right side upper butt pain..right pelvic bone srea pain..thigh strain..back pain worse when lying down straight..its been a week..possible causes?

Back pain: Pain in the area of the upper buttock along with back pain may be due a problem in the lumbar spine. If the pain is positional, better in some, worse in others, it suggests some mechanical issue perhaps a lumbar disc prolapse. There are other causes of pain that are not neurologic, and worth seeing your doctor for further evaluation and examination.