I weighed 108 for the longest time, and was so worried. My doctor told me to keep taking my vitamins, and that my body would do what it needed to as far as weight gain. I'm 33 weeks and have gained about 30 lbs so far, and honestly I haven't changed much in my eating habits. Basically, I eat what I crave (within reason), eat when I'm hungry, and stop when I'm full.