Weight gain during pregnancy 32 weeks

I am 32 weeks today and read that the average weight gain for 32 weeks is 27lbs. At my 30 week check up I only gained 20lbs. I had the Stomach flu on Monday and Tuesday last week lost 3lbs because I couldn't hold anything down. I go to the doctor this next Monday for my 32 week check up to see how much I have gained. I only weighed 103lbs pre-pregnancy. I'm worried that I'm not gaining enough weight for my little girl. Is anyone else worried that they aren't gaining enough weight? I don't want her to be under weight when she gets here. Is there something I should do to help gain more weight? My doctor doesn't seem concerned cause I was so small when I got pregnant but I can't help but worry for the health of my little girl.