Talk to your OBGYN (you are going, right? You need your prenatal vitamins and everything. Don't wait on this.)
You don't seem like you are very overweight at all. Going on a diet to lose weight while pregnant is usually a bad idea unless the mother is severely overweight. You will gain some weight during pregnancy anyway. Worry about it after you give birth. In the mean time, just eat healthy: fruits, vegetables, whole grains, dairy, lean meats (careful of the fish because of mercury and no sushi!), etc.
Don't forget to make an appointment with you OB. Also, congratulations on your pregnancy!