Well I know when I eat a lot, my belly has a growth spurt... LOL
Its true though, and not just in a "getting fatter" kind of way. I have had a few 2-3 day spans when I'm just ravenously hungry all day, and even if I don't gain a single pound on those days my belly still gets bigger!
I've heard that they go through a growth spurt between 16-18 weeks, then 26-27 weeks, then again at 31 - you're right at the 26 week mark almost, so maybe it is a big growth spurt kicking up!