To answer your question, yes, AS can be very difficult to diagnose. Reactive is one of the spondylitis diseases. I'm not sure what I would do. If it is inflammatory such as spondylitis, then you are smart to encourage exercise. Swimming is great. Perhaps it would help to watch the webinar SAA held last weekend. Sorry to hear whats going on. I hope whatever it is goes into full remission soon. Sending prayers now.