Headache from Hell

I have the headache from hell today. It started last night with a slight annoyance in my right neck muscles. This morning, I had a little bit of sinus issues, and chalked it up to a few draft beers and a smokey bar last night. Then, just before lunch, it got bad. So bad that I thought I might die. All centered on the right side. Then, as quick as it came, it was gone. Now, 4 hours later, its back, but on the left side. Is this a migraine? Or is my head really going to explode?