A Quick Question for my Knowledgable Readers

So, I'm taking my Prometrium twice a day, like I've done the last two cycles.  Except, this time, I think it's causing me headaches.  I started them Sunday and Sunday, Monday and today I've had headaches for at least part of the day.  It seems like I've heard of this being an issue, but I can't remember for sure.  Also, I just find it odd that I've never had this problem either of the other cycles that I've used it. 

Any advice ya'll have would be nice!