I had some dizziness as well in the first half of my pregnancy. You have a lot more blood when you're pregnant and that is part of the reason why. It can pool in your legs and make you dizzy when you stand up too quick or if you stand in one place for a while then start to walk. You can also have low blood sugar a lot quicker when you're pregnant I think and that causes dizziness especially if you don't eat regularly. Just make sure you're eating healthy and drinking lots of water and getting enough iron so you don't get anemic. If you're feeling faint though, I think that's probably a lot more serious and you should check with the doctor.