Perhaps speak with your Ob/gyn on a calorie plan for every week/semester. This is not the time to diet, you want to make sure the baby get all the necessary nutrients and grows healthily. Interesting fact, first pregnancy I gained 25kgs, eating really healthy, no fizzy drinks etc. Baby weighed just over 3kgs. Second pregnancy only gained 10kgs, also super healthy, baby weighed a very healthy 4kgs and had caesarean at 38 weeks, imagine full term. So picking up a lot of water weight/weight during pregnancy does not guarantee a big baby, and gaining a small amount during pregnancy does not give a small baby.