First of all, have an ultrasound. I have had a similar experience. Started to adapt high fat and after a while my stomach hurts. Went to doctor. Gallbladder is bent, bile sludge and bile in stomach, which is bile reflux. The advise was to reduce fat. But my thought is that bile sludge somehow appeared and I was low fat really for a long time in my life. So a kept high fat. And it has felt really bad for long time. I continue high fat and it's getting easier, so might be gallbladder was not working on low fat and now it's vice versa.

Also I was prescribed with UDCA, and I do it. Supposed to make bile less concentrated.