i pm u my chi doc's infor. i faced a similar problem. after eating the thing my chi doc advised, the bb grew more than 1 pound in the past two weeks but i remained in my previous weight.
My due date is also around end of Jan, my BB weighs 1.75kg when I saw the doctor on last Friday (1/12) and I was in week 32. She said the BB size is normal. Besides, as I learnt from the book, BB size is around 1.7kg at about week 32. So I think you are okay wor.