The first day of my menstuation, I experienced extreme cramping in my lower abdomen, followed by vomitting, diarrhea, and faint-like symptoms (lightheadedness, white-outs). This happened just following an Equipment Pilates session (Reformer). I laid on the bathroom floor for 30 minutes or so; and preceeded to lay down for an hour. For some background, my cycles have been irregular since getting off the Pill April of 2010, between 27 and 50 days, and I have PMDD (but never this short-lived, vomit, fainting condition). What could this be caused by?