7 weeks: 12.8lbs
7 weeks, 2 days: ~13lbs
7 weeks 5 days: 14lbs
8 weeks 2 days: 14.6lbs
9 weeks 1 day: 15.4lbs
10 weeks: 19lbs
10 weeks 5 days: 20.5lbs (weighed in the evening after dinner)
12.5 weeks: 25lbs
14 weeks: 30lbs
20 weeks: 37lbs

He'll be 21 weeks on Saturday. His growth has slowed a lot, looks like he's behind most people for his age bracket. He's skinny, though, so that might account for it.