My measurements went down, that's due to the bay's head being down. Also called "lightening" or having the baby "drop down". It means she or he is practicing the escape route position. My baby has been head down for 3 weeks. I've only gained 22lbs, and am 37, almost 38 weeks along. The doc says 7 1/2 pounds give or take.
I was 6 lb 5 oz. My husband had to make me freak the other day by telling me he was 10 lbs! Chances are the baby is fine, and weight is normal. Have you had a ultrasound lately? I got one at 8 months, which was routine from what I understand. They can guage the weight from that.