This is an interesting question I've often wondered similarly. But mine is a little different. Mine doesn't come before it's the 5-7 days of mother nature's gift/curse. It was a joke (not funny. It was mean) in my family that I didn't have pms I had dms. And when it hits it can go either direction. It doesn't last long, but long enough to say something's wrong then it's gone. I'm going to bring it up to my Pdoc next visit to see what she thinks. I don't think it's normal to get these symptoms during the flow. Sorry ramble. Thank you for bringing this up.