First, see a doctor to make sure what the problem is.
Some of the PTs, MDs, DOs, and chiropractors around here reccomend these stretches
http://www.spine-health.com/topics/c.../sciaex07.html for sciatica and SI injury. Also somewhat helpful for problems with the psosas muscle (a frequent cause of sciatic type pain).
You are correct, for this kind of pain, medications too often don't help. Sometimes anti-inflammatories are good, sometimes not. Actual analgesics aren't much help for most people though.
Good luck getting this straightened out. With effort and persistance with your stretches and proper exercises, it can be done.