Nausea is a normal part of your period.
One of the hormones released during your cycle is called prostaglandin. Though most of it sheds with the uterine lining, some gets into your bloodstream. This can cause nausea, vomiting, diarrhea, and headaches.
Many over-the-counter pain medications such as ibuprofen and naproxen cut down on prostaglandin production and may help ease these symptoms as well.