I'm nearing the half way point :)

I'll be 20 weeks on Tuesday, September 28th, 2010. I've gained just 8 pounds, so I feel good about that. I was reading somewhere gaining 10 pounds is average for 20 weeks. If I've only gained 8 pounds though, where is it all coming from? My belly is huge. Which makes me wonder, if I'm this big now, how big will I be in a few weeks?