My back is in extreme pain after standing up for almost 9 hours straight, help?

Core Exercises: Typically core strengthening exercises are the best to help relieve pressure and forces in the spine. I would try and google some or look them up on youtube to see descriptions. If you can do them yourself, wonderful otherwise ask your doctor to get a referral to a good physical therapist for further assistance. If still hurting after that i would see a pain/spine specialist for full evaluation