With my 2nd, I lost 12 lbs before gaining. With this one (3rd) I gained my first pound at 25 wks. As long as you are eating healthy and your uterus is measuring right then your Dr should be fine with that. I started each pregnancy at 195lbs.
Are you nauseous and throwing up often? That could be normal. Heavier women tend to not gain as much weight and some may even loose some. Just eat healthy and try light exercising like walking to stay health. Also if your medical provider hasn't mentioned it you shouldn't be concerned.
Women who tend to weight more dont always gain wait. Or they will lose it. As long as you are eating enough of what you should be then I honestly wouldn't worry too much. But I'd def ask your doctor.