I heard this can happen in the last months because of the size of the baby making you feel full faster.
I have had to eat such tiny portions for the past 2 weeks and now that the baby dropped I can pack it in again.
It could also be that you were retaining water on top of not eating a lot. I know that being pregnant and forgetting to drink enough water can cause that along with constipation.
Are you using the same scales? I weighed myself using the scales at Publix (grocery store if you're not familiar with it...they usually have big mechanical scales in them) a week ago and I was the same weight I was 4 weeks ago...so it kind of worried me, and then I weighed myself yesterday at a different Publix and I had gained 6 pounds. I think it's more likely the scales were different.
Also home scales are usually really unreliable...and even some scales they have at the Dr's are unreliable. I always weighed 4 pounds less at my previous OB's office than anywhere else.
I know I have lost weight the past few weeks. I am not as hungry, I feel full faster and know that I am not eating a heck of a lot as what I used to....that added with the greater demands on my body that this baby has - of course you will lose some weight!
I know I haven't lost 7 pounds, but I have lost some. The baby is plenty energetic and obviously growing, so I'm not concerned. It actually makes me a little less worried about losing extra weight post-partum if I'm losing some if it now I'm not sure if it's normal or not... none of the recent moms I've talked with mentioned losing weight at the end, but though I can't eat lots, what I do eat is balanced and healthy, the baby's doing fine and I feel good.