When I was pregnant I was extremely light headed. My BP was often on the low side (generally about 90/50 no higher than 110/70) even with drinking heaps of water. I read that during your second your blood vessels dilate in response to the pregnancy hormones, allowing for a greater blood flow to ur baby and placenta. It's a common symptom in the 2nd trimester. Lower blood sugars could also be something to think about, try to eat regularly so that your blood sugar never drops too dramatically. And try to avoid things like standing up too quickli