Here is my somewhat brief story and experience with this. I was diagnosed in November 2018 with this after suffering from really bad back pain that would originate in the middle of the night and subside about an hour or two after waking, every single day since March of that year. I started seeing docs in May that year (PCP 3 times, spine doctor, chiropractor, physical therapist). No one could diagnose the issue, or why some other issues were popping up (random joint pain, neck pain, plantar fasciitis, achilles pain). However, my physical therapist did state my SI joint was the source of some of my pain that was going up to my thoracic spine. I googled this and came across AS so I made a rheumy appointment who quickly was able to diagnose me after an SI joint MRI and positive HLA-B27 gene.

Here is some of the fallout:

CRP and Sedimentation lab tests are normal so he suspects my case is mild, however I am monitored every 6 months with these tests. X-rays from my SI joint to my neck show no fusing. I have tried natural methods such as the autoimmune paleo diet, turmeric supplements, etc. None of this helped. I've been prescribed Celebrex 200mg daily which has greatly improved how I feel. Stress seems to be my biggest flare up trigger. While I know taking an NSAID every day isn't good, I don't really know what else to do because the way I felt before was misery. I try to mitigate the side effects by taking it after a meal followed by lots of water.