18 weeks today and still have not gained a single pound. We had an ultrasound yesterday that showed baby measuring exactly 18 weeks (based on measurements of the femur, humerus, abdomen, and head). So I feel confident that baby is getting what she needs despite my lack of weight gain. I do expect to start gaining from this point forward, although we'll just see how it goes. I'm sticking to eating when I'm hungry and making every calorie a nutritious one.