I've had similar flares where it can take me up to 20 minutes to get out of bed because I can't move my back. I try rolling left or right (I sleep on my back) until I can finally get on my side. Sometimes the pain is so excruciating I'm in tears, and sometimes my costochondritis flares at the same time - the first time that happened I was certain I was having a heart attack! Thankfully, I wasn't.
My flares can last several days or several months. When I first started having symptoms I was in my late 20s and I was diagnosed with Chronic Sacroiliitis, but no referral to rheum. Now I'm in my early 50s, I'm still not officially diagnosed, and my flares are more frequent and more intense than they've ever been in the past - or I'm just getting older and maybe my tolerance after 20+ years of chronic pain isn't what it used to be.
I've tried a lot of different things - anti-inflammatory diet (hard to quantify whether or not it's working, but I'm able to maintain a healthy weight on it), chiropractic (been going since my late 20s, and it may be why I've had little progression), acupuncture (helps with pain during a flare), massage therapy (no bueno during a flare), posture braces, insoles, new mattress trials (yes, for a while I even thought my bed was the culprit!!), meditation, mindfulness training, anti-inflammatory herbal tinctures. You name it, I've tried it! If someone told me skydiving would help, I'd give it a go! I've found it's a lot of trial and error and what works for one person won't necessarily work for someone else because every body is different. One of the worst things for me during a flare is getting up the stairs or trying to pick up something off the floor. It's painful and frustrating. I have to make freezer meals when I feel well because I can't "make myself" cook during a flare. One of the pitfalls of living alone, I guess.
One of the pitfalls of rheumatology in my experience so far (I've been to 3) is that if you mention "spondyloarthritis" they automatically jump to AS (ankylosing spondylitis) despite there being an entire spectrum of spondyloarthropothies. I've yet to have a rheumatologist want to diagnose without strong imaging support (I don't have that), a positive HLA-B27 (I'm negative) or a blood test showing inflammatory markers are high (not everybody has these, especially those of us who have had chronic inflammation over many years - there are studies that support this). What I do have is a strong family history, early insidious onset (27 with no injury or strain to attribute the pain to), pain lasting more than 3 months that improves with movement but not with rest. I also have costochondritis and enthesitis, so it really shouldn't be this hard. In any case, I wish you all the best and hope that you are able to get a diagnosis that can provide a treatment that will bring you the relief you deserve!