I wouldn't worry as every woman gains weight differently during pregnancy-even sometimes with subsequent pregnancies. I am one of the ones gains all on the front. From behind, I don't even look pregnant, until I turn. And with less than a week left, I have a 48" waist that was once a 31" waist. A co worker of mine gained all of hers in her hips and behind as well as her face. She had the same complaint as you saying she didn't really look pregnant-especially working beside me. She delivered 3 weeks early and her daughter was 7lbs, so I wouldn't worry too much. If it is really bothering you, I would bring it up to your Dr. next appt. Have you had your ultrasound yet? They measure the head circumfrence and various bones etc. to see how well baby is developing so they can rule that out for you as well.