Pre-menstrual symptoms.

I suddenly lost my appetite for a few days. Yesterday morning, I really didn't want to eat anything, so I only drank water, went to the library, and took a walk around the neighborhood. Even at lunch, I had no appetite, but I bought and ate some jajangmyeon and jjamppong on the way. I was with my older sister, so I ate happily... but why do I have no appetite? I experience these symptoms right before my period. I don't have menstrual cramps, but I have no appetite. What symptoms do you experience right before your period?