You really shouldn't worry about weight, I don't think it means anything really, because people show weight in different ways, some girls look heavier and actually aren't, or vice versa it's just dependant on the person and all types of things make you look skinny/curvy (height, muscle, fat etc)
7.5 stone
5'4
UK 6-8
34B
Usually I'm a six in tops and a six in skirts and dresses (probably just because of the things I wear, skirts sit on my waist, which is really small) but jeans I tend to be an eight because they sit on my hips and are skinny fit.
I'm quite self concious about my weight, I tend to get a lot of comments on it because I'm small and people seem to think being insulted on your weight is only upsetting if they call you fat.