I have pain that goes from hip to hip down into the buttocks, and I have pressure and some pain in the pelvic area. Could this be sciatica?
Only a doctor can tell for sure but, yes, sciatica commonly does cause symptoms in that area.
The main symptoms for sciatica are pain from the low back to your buttock and then along the back of your thigh and calf, numbness or muscle weakness in your leg or foot, pins and needles feeling in your toes and feet and rarely,a loss of bladder control.
You might want to try Health Centrals "Check a Symptom" program and see what it says about your pain. Good luck!
Here are some other links that you might find helpful:
Sciatica – An Overview
Disc Herniation: What is It?
Back Pain and Sciatica