Frustrated!

I'm 20 weeks with boy/girl twins. I was really thin before getting pregnant so I'm extremely uncomfortable now. I'm getting so frustrated with women who have never had multiples before saying things to me like "you're only 20 weeks, just wait until you're farther along". My 20 week twin uterus is measuring 30 weeks. I know it's sounds silly for me to gripe about but it's so annoying