I just recovered from the stomach flu, why do i have shooting back pain only when i am standing or walking? i cannot get up

Pain: It is hard to make a diagnosis without proper history and physical examination. However if you just suffered a stomach flu i assume that you were in bed for extended period of time. The back pain that you are experiencing could be due to musculoskeletal origin. Perhaps stretching and massage may help. If it persists or worsens check with your primary doctor for proper diagnosis and treatment.