Azwoody said...and you tend to look fat in clothes!
Untrue. If you look fat in clothes and you're in good shape, you're wearing the wrong clothes and fit. Honestly.
Either way, I understand the point of view of the OP. Once you've worked out your body, it's natural to want to improve the parts that you feel are "lagging." Genetics play a role though. Some people are just genetically built to be bigger in certain areas than other.
Case in point, my best friend is always complaining that he wants to have a chest like mine and keeps asking me what I do for it. I'm 5'5" and my chest is about 43". Add to that the fact that my body has a natural hourglass build that I can't change and it just makes it all look bigger in comparison (my waist about 27.5").
I keep explaining to him that I have done absolutely nothing different to my chest than to the rest of my body. I work my entire body out equally to avoid muscular imbalances. It's just always grown that way. Even when I was thin, my chest was never flat.
He doesn't notice though that he has absolutely GORGEOUS arms, which I simply can't pull off. I have nice arms: in good shape. But his just grow amazingly huge and rippled. He's genetically made that way, but he doesn't seem to notice it.
My arms lag behind no matter what I do. They're very strong to a point where I can do strength-related things that are great, but as far as muscle hypertrophy goes they refuse to grow the way I wish they would. I've tried everything and seen decent results, but not quite what I want. I think I'm just genetically made that way (different muscle fibers, probably).
Basically, there is nothing wrong with trying to improve lagging body parts (and someone already gave good advice on it), but remember the role genetics play. Above all, remember that you already have an absolutely beautiful body, even if your chest isn't massive or as big as you want it. I'm sure there are PLENTY of things your body has that other people wish they could have. Work on the things you want to, but don't forget to love what you have and work with that.
It seems like a non-answer, but usually I find that people's biggest issues with their body stem purely from attitude. People just become accustomed to being in good shape and suddenly it becomes "the norm," and forget just how amazingly beautiful they look.