Back in the 90s, I started having a lot of...digestive upset. Mostly pain after eating, but also back and forth between being constipated and being anything but! The doctor suggested one thing after another and I "treated" it based on the guess of the moment. Numerous friends told me to have my gallbladder checked and I couldn't imagine that being it - I was too young for that!
I started not being able to keep meals down, dropped 30 pounds in a few months (and yes, vain enough to actually like that), and spending hours standing with my head leaning into a cool corner in my hallway while I tried to concentrate on making my body relax.
Finally went back to the doc and suggested she check for gallbladder. And yes, of course, that was it. When they got in there and removed it, it was so infected it might have been just days/weeks away from going gangrenous.
It was relatively simple surgery and was back to work within 3 days.