Hi there,
I have also been having similar spine pain, and I mentioned it to my rheumy at my last appointment, but he didn't seem too concerned. However, in July I was diagnosed with Osteoporosis, and my pcp forwarded the information to him, and now he seems very concerned about my spine/pain. I have a feeling at my next visit I will be getting an MRI to check things out. I was asked at the time, if I had any numbness in my legs etc and I said no, so he didn't suspect AS. I do have the bladder inflammation or IC.
Hang in there and I hope you get an answer soon.