So ladies I’m having issues I’m eating sooo much but i can not gain weight and now the dr says my…

So ladies I’m having issues I’m eating sooo much but i can not gain weight and now the dr says my amniotic fluid is just a tad low ,she suggested G2 and water but I’m worried i had problems last time gaining weight and i had a premie . I’m not a small girl by weight but my stomach never gets that big... so i really need to know what i need to do ? Help if anyone has advice