I have a lot of back pain from my JRA. Other reasons for back pain can be that the inflamed bowels are putting pressure on your back. From my understanding, AS is more rare & is more prevalent in males. I don't know much about Facet Syndrome but AS can be DX via xray/MRI(it may take a while to show up). A friend of mine is undergoing testing for AS because her Crohn's is so severe that her spine is curving into a D shape. Very painful stuff!
I go in my hot tub, take a nice long WARM epsom salt bath, use heating pads, heating blankets & run to help ease the pain. If you don't feel like running, do stretches and walk. It will help you out in the long run & provide more flexibility if you have AS.
Take care!