No one else in the family was having it, so I was thinking I had some kind of organ failure
or something! Yikes.
I kept googling, though, and
found that there is a fish called escolar that causes this phenomenon. It is often sold under the wrong label (orange roughy, cod, sea bass, white tuna), so you may not know you have eaten it. This fish cannot process certain esters, so it stores large quantities and human consumers excrete them. I don't know why the rest of my family has had no problem.