I was diagnosed about 12 years ago with ankylosing spondylitis. My journey started out with degenerative joint disease and as damage was done through the DJD and osteoarthritis and a few other diseases & conditions I received the ankylosing spondylitis diagnosis.
The exercise is what I have found helps the most to ease the pain and help me maintain flexibility and to keep the flairs at bay. Of course there are times no matter what I do the flairs hit. When the flares hit I use heat and ice and nonsteroidal anti-inflammatory drugs (NSAIDs) but I have to be careful using the NSAIDS because they can cause stomach issues.
For me it is doing whatever I can to keep the inflammation, pain and stiffness to a point I can tolerate it and that is where the ice, heat, and exercise come in to play. I have found soft yoga to be a big key in keeping the stiffness low.
Due to my other diseases and conditions I am on several medications but have found Meloxicam (Mobic) to help a great deal.
I totally understand about trying to figure out if it the fibro or the ankylosing spondylitis. When you have multiple illness or conditions it makes it hard to know which one is acting up and causing the increase of pain.
My best to you,