How to go from "loving mom" to "monster mom" in 20 days...

It's called PMS. (Sorry guys, this post is a bit "girly") What has happened to me? I used to be proud of my monthly sanity- I never had a problem with PMS. But- something has changed. Some kind of evil monster takes over my life once a month. It seems to have started since I became a mother- or maybe since I became 30, or maybe...who knows. It's just been sometime in the last few years. Sometimes I catch on that the monster has arrived and sometimes I don't realize until it becomes hindsight. Last week, I was a horrible mother. Especially on one particular day. So, I just went about my day, figuring- I was a horrible mother. A few days later, a little trigger made me realize.... "Oh brother, I was PMS'ing last week." How to go to "monster mom" in 20 days? Just ask my family. It takes no effort at all; it seems to come naturally and seems to strike with deadly venom. I dont' know, maybe I should just go on vacation once per month. Sounds good to me.