I don't consider myself too incredibly thin, but pretty average/small boned. As of 32 wks I've only gained 14 lbs. I think the comments from outside sources about how much THEY gained and am I SURE I'm eating enough have contributed to some anxiety on the subject. I just don't gain more than approx 15-20 lbs w/ pregnancy. I don't know why. I love to eat, and do it whenever I want! My other two pregnancies I gained almost 20 and approx 15 lbs, and those babies were 6'11 and born at 37 weeks......and 7'4 born at 41 weeks......
Not sure if that helps at all....but it's something that's on my mind as well. Are you measuring small? I've been anywhere from 3-5 cm behind in FHM the times we've measured and this is a regular thing for me......