7 months I feel like my bump is so small!

I'm 7 months and i only gained 3 lbs so far. I feel like I'm so small but when I went to the doctor he told me I'm measuring a little bigger. I'm confused. He also said it probably because I'm short. What do you ladies think? I'm scared I'll blow up at the end. Lol. So many people can't believe I'm 7 months. These pics were taken all this week.