Mysteries of Pregnancy Theater 3000 - Episode 1

I'm now 15 weeks, and my waist has grown from 29" to 32" during that time. I'm measuring from the belly button. I'm not sure if that is the right thing to do, but it's the only way I could figure out where to measure consistently. So, my waist has grown 3" around at the belly button. Here's where the mystery starts...the baby is only about 3.5" big. To really see that in perspective, you need to look at a ruler. Three and a half inches is not very big. Could I not just fit that 3.5" into the existing space???? I don't need to be growing yet. The good news is that I haven't put on any more weight. That's super good news since I have to go to the midwives next week, and I don't want to get yelled at for gaining more than the 8-10 lbs that I'm allowed in the first 20 weeks!