20w pregnant with no weight gain, frequent dizzy spells, shortness of breath, palpitation (normal eating). baby measure normal on level 2 ultrasound at 19w. do i need to worry about low weight gain?

Be watched closely: I've seen some women with little weight gain during pregnancy have perfectly healthy babies, but weight gain of about at least 25 pounds would typically be expected. Make sure your doctor monitors closely your fundal height growth, and probably also more ultrasounds that the typical pregnancy for closer monitoring of the fetal growth.