Hi. I have the same issue at 7 weeks. I think it's due to blood pressure dropping which happens right through til mid pregnancy, when it starts to increase again.
I'm almost seventeen weeks and have had NO morning sickness whatsoever and as far as we know things are going swimmingly - good luck!
You could be low on iron. They can check you for that. With my 2 pregnancies years ago I had to take iron pills 3 times a day and it helped with the dizziness.