My history may help others.  For three years (in my early 20's), I experienced severe back pain (upper middle back).  I even completely rebuilt the drivers seat on my new car because driving was nearly impossible.  I went to orthopedic specialist.  He sat me down in consultation and said he was certain I had AS.  His prognosis was gloomy and my future bleak.  His advice was to get life insurance and to be as active as possible.  I was depressed for several months.  Over the next few years he prescribed several different pain meds.  Not much success.  Each year he took x-rays and did measurements with calipers and he always measured my chest .  The pain stabilized at fairly miserable.  5 years later, I experienced a serious afib event.  The heart specialist after many tests asked me if I had ever been told I had AS.  My dad had recently died of a heart attack.  I assumed I was next.  That same day I decided to "bring it on".  Heart attack or bust.  I started running cold turkey.  I didn't have a heart attack, so I really took up running and being very active.  Over the next several years I would experience a painful separation of my rib cage when I would relax in the evening.  Also, my sciatic Joints would painfully "split" for about 20 minutes when I would lay down.  I had quit seeing either doctor and started taking 12 to 14 aspiring a day.  (You can call me idiot if you want).  (By the way, this is a 45 year story with a positive outcome).  I ran and took the aspirins but eventually, several long bad flareups sent me back to the specialist.  Back to square one...he was half retired and his records were in storage.  I felt like I had no support.  My best relief over a 10 year period was to have someone walk on my back and literally "break" the vertebrae loose.  This is not likely to be recommended by any doctor but the pain was so intense....I did not care.  My family doctor tried numerous pain meds.  Eureka.....vioxx was my miracle drug.  My doctor said it was high risk for heart issues but worth it for a quality of life.  I had a half dozen good years.  Then the government pulled vioxx off the market for those heart issues.  I had one really bad year.  I thought I would have to go on disability.  Finally I went on celebrex which had the same risk factors as vioxx.  The pain was always there but stabilized.  

Over the years, I have developed a pain threshold much higher than most people.  I believe that If the average person were to experience what I experience every day, they would be in the emergency room.  So, here I am at 70.  I am on celebrex (tones the pain down).  I can't crack my back any more because several vertebrae have fused.  It doesn't show and actually hurts less.  I still jog (will do several half marathons this year).  I am still active.  Oh, and by the way, I have slept on the floor for the hard surface for the last 10 years.  When I have flareups, I have a flat ice pack that I sleep on all night.  The hard flat pack and the cold directly on the bad spot really helps.  

Here is kicker to this story......I actually feel lucky.  In the past I experienced a lot of pain.  I developed a high tolerance for pain so that now it is acceptable.  I get good sleep at night.  I have remained active so I am not stiff.  And I can still run.  I do not believe I project my affliction.  Like my original doctor said, "stay active".