What Causes Headache, Dizziness, Nausea, Lower Abdominal Pain And Blurred Vision?

I've had a head-pounding headache since last night and also woke up with it this morning. I went to school and started feeling dizzy and nauseated and started seeing black spots, and my vision was just all in all not right. I got my period today and also have really bad pain in my lower abdominal region. Is this a normal side effect, or more serious?