You are right, gallbladder is right side.

Spleen is upper quadrant, pretty close to the bottom of the rib cage but not super far fetched if you have a short torso. Had to know exactly where when mine was swollen with mono, it is huge rupture risk. Since it was 13 years ago I cannot remember if my stomach ached but I have the same pain you describe every couple years.

Is it possible you carry Epstein Barr like 95% of the world? That could trigger mono which triggers swollen lymph nodes, spleens. How are your glands feeling? I was not super fatigued with mono, oddly enough.

One weird thing my husband found before getting diagnosed with crohn's is you actually have lymph nodes in your stomach that can get inflammed with strep viruses. I don't know why but it sounded weird to me at the time. Do you eat probiotic (is that the term)? His gastroenterologist cannot sing the praises of yogurt and good cultures highly enough.