i had the same problem until 2 weeks ago.. i have had bad ms, and lost lots and lots of weight.. but 2 weeks ago i had a very bad flu and am still suffering from very bad cough, add to it i broke a grinder while eating dates!! so DH got crazy and blamed it all to my weight loss and not getting enough nutrition so my immunity is zero plus that the baby is sucking nutritions from my body -from my teeth and thus!! so now i literally am forced to eat for 2!! and BOM i started gaining weight like quickly!!
i used to think it is ok as i have read tons of stories about women who didn't gain a pound during their pregnancy, but now i would really suggest that you ask your doctor to see if your weight gain is fine.. i was having lots of issues till i started gaining some weight.. how is your vitality? are you feeling ok overall?
according to most charts you should have gained 6 pounds by now, i have read that most women have higher metabolism during pg, and that you need to add 200-600 calories to get a balance diet!!