I am 33 years old and for the entirety of my period-having life, I have always gotten an unmistakable feeling the day or so before my period starts, like a mild version of period cramps that lets me know it is about to begin. However, the past two menstrual cycles, I have had zero warning. I just wake up covered in blood. And even then, the only reason I know to check for my period is by the wetness. My cramps do eventually come on, but as I said, this is a very unusual thing for me: I have absolutely always had about a day of warning and then my period starts as spotting. Now there is no warning at all and it starts full force. What could be the cause of this change?