Sparkels
I am not a rhuemy so would fall short of trying to diagnose you from an internet post although the symptoms / problems you describe are certainly familiar, basically a deteriation of lumber spine and inflammation of the sacro iliac joints (between the sacrum and ilium of the pelvis).
One of the main hallmarks that seems to set AS apart is Iritis. Have you had bouts of this problem?? This can almost clarify the confusion.
Unfortunately with AS being the disease it is, and sad misunderstanding within the medical fraternity about it, you may be best seeking a number opinions from other reputed specialists in the area.
Coming from one who virtually self diagnosed I also found personal research quite revealing albeit very stressful because you jump to sometimes wrong conclusions.
Find a rheumy who listens, is well informed and expwerienced with AS. That'll help a lot.
Good Luck
Jonno
