I'm not getting pms, but I always do

About a week before I get my period I start getting pms, cramps, bloating, mood swings, etc. But I haven't been getting pms this month and I'm supposed to start tomorrow... No symptoms of my period at all. I've had a migraine for a day and a half now and idk if it's the reason why I'm not getting pms. I'm very regular, I've had my period for almost 2 years now and I've always got it around the same time each month. I can't be pregnant, and I've always got my period no matter how much stress I'm under (I've been under a lot more stress than most people but I still flow regularly) i haven't lost weight recently and not a lot has changed in my life for the past few months. Any one know what's wrong with me?