Weight gain question

Amanda • Married 9/28/13 due with baby #2 in Jan!
So I'm 18 weeks and have only gained a pound. My belly is growing, but still a little nervous that I'm not putting on enough weight. I do workout daily and eat a clean diet, but everything I read says you should be gaining 1-2 pounds a week from 14 weeks through the rest of pregnancy. Anyone else having weight worries?