Pms??

So for the past few days I've been pretty emotional and I really don't why. Like I was just watching this video about a mom who lost her daughter and the daughters heart was given to another lady I started to cry. And then my husband said he was going to watch a movie and I got all mad at him. I'm about 11 days away from my next period so why am I so emotional? 
(Sorry if this is a stupid question lol)