Everyones different some new mommys lose & others gain. Eventually your body will catch up until then check w/ your Dr.
When I went in for my appointment today, I had lost 6lbs since last week! My doctor said that it was not much of a concern in the first trimester and suggested that in addition to my prenatal vitamins that I might also consider a DHA and a folic acid supplement. Good luck and congratulations, hope you are feeling better soon.