Hi KB,
Welcome back...though I am sorry to hear of this current challenge.
It is most likely muscular, like you suspect...either the mentioned obliques, or perhaps intercostal, with referred pain felt lower into the hip.
I would continue with the ice, and a NSAID (if tolerated) to reduce inflammation and pain. I am a sure with this regimen, you'll be feeling better soon!
Use your positive mantras and maybe work some Therapy Worksheets to combat the 'what if'/catastrophic thoughts.
Update us soon...we are sending healing thoughts!
S.C.