What Causes Headache Around Left Eyebrow During Pregnancy?

I am 21 years old and pregnant with my first child. I have had a headache around my left eyebrow and behind my left eye on and off for about 2 weeks now. It seems to get worse when I lean down or turn my head. They can last a short period of time or last for hours. What could it be and what could I take to help these headaches?