Ankylosing spondylitis?

I’ve been running a lot for about 15 years now, off and on, and at about age 28 I started getting this dull lower back ache that would come and go, sometimes sticking around for weeks without end. It’s not exactly progressing rapidly, but it’s also obviously never going to go away. It took me years and years, but I finally think I’ve figured it out. It’s the above, an autoimmune disease. Interestingly, when I go keto it disappears completely, and when I start eating carbs again, it comes roaring back. My case is mild, and I’m not here to complain. I’d just like to ask if anyone else has experienced this, or knows someone who has, and whether you have any insight into the condition and potential treatments. I’ll hang up and listen.