Is there such a thing as post-menstrual syndrome? i've noticed i sometimes experience pms-like symptoms (emotional, anxiety, etc.) toward the end of my period and sometimes in the 2-3 days immediately after it ends. why is that? hormone changes?

In the mid to late 30's , women's fertility rate decreases as eggs become less amenable to pregnancy, and the ovarian stimulation necessary to achieve ovulation increases, producing higher estrogen levels. The pharmacologic effect of rapid decrease from a much higher level creates emotional consequences, and lasts until estrogen levels increase again with the onset of the next cycle.