As long as your Dr. says youre okay, youre good!
When I showed up to have my son they asked why I was there I was 35 weeks. some people just stay small Dont worry :)
I'm 23 weeks 2 days and I also am feeling the same way you are. Every pregnant women is different. As long as your Dr says everything is okay then girl don't listen to anyone else. There's nothing to worry about.
I feel that way sometimes but it makes me happy cause I tell myself maybe ill be smaller after I have to baby. I'm 3 weeks and gained 3 pounds thus far