Hey Shanno! Sending cyber hug ...
I feel your pain, I have the Royal Pain in the Butt too.
I don't have AS - well, no fusion anyway - just persistent SIJ inflammation for 18 months plus a brief bout of iritis. I seem to have low-ish level pain all the time (much more at night) with a few really bad days every couple of weeks, with nerve pain down one leg. I don't really know why, I'm always trying to figure out what brings the extreme pain on.
Tried the cortisone injection a few months ago and found it alarmingly painful but only for a few seconds. Lots of muscle spasms too, but it didn't last. I seem to have gotten a bit more mobility since then, though it didn't really reduce pain.
I've found Naproxen (NSAID) good to reduce the pain - by maybe half. Also tried Mobic but it didn't do very much and gave me bad heartburn. My rheumy prescribed methotrexate, added to sulfasalazine. I was kind of hesitant to start methotrexate, but so far haven't really had any side effects.
I'm a big fan of physiotherapy, I feel much less bound up after a session. Took a while to find a physio I really liked, it was worth the effort of shopping around. Also being in or walking in a warm swimming pool. Even if it's too painful to exercise much, it's really soothing, calms me down anyway.
Are you going to be prescribed a TNF blocker drug? I've heard they're a miracle for some people.