I'm having very low left sharp and steady abdominal pain. i've had groin pain related to si joint problems, but this is more low abdomen. i have ankylosing spondilytis, but this isn't spinal. no bloating or other issues. i'm not sure how to treat?

At your age and with the pain location, acute diverticulitis is strongly suspected. Physical exam, blood test and CT of the abdomen will confirm the diagnosis but not always necessary. Recently, studies have shown that antibiotic(s) may not change the outcome in mid to moderate cases. You need to hydrate well in the mean time. Go to the hospital if pain gets worse or high fever & chill occur.

Best is to see your MD as this seems unrelated to your other problems. Good luck.