I have these occassionally too... In fact, I just had one last evening. It certainly doesn't help when you have a DH and DD who just want you to be happy, and are trying everything they can think of to make you laugh.

I just want you to leave me alone!
(all better now though)
I had preeclampsia with dd, and I definately had headaches with that too, but they were a lot different than what I experienced yesterday. Preeclampsia headaches are "foggy" dull headaches. I remember very little of my last weeks of pregnancy with dd because I was just so 'out of it'.
When I had her, the next day I felt like I had just woken up from a very long doze. It was really odd. I'm hoping I don't develop that with this baby, so I'm trying to take very good care of myself and keep hydrated, etc.
Your MW/doc should be keeping a good eye on you anyway while your getting prenatal care, but if you are still concerned, a quick call to them wouldn't be out of line, especially if this continues for several days.