girls 5'5" at a healthy weight?

i'm 5'5" and am underweight. i know how much i weigh and what i want to weigh (more or less), and completely understand that everyone is different. but i still want to ask: if you are medically at a healthy weight, what size do you wear, what is your weight, and are you happy with this? just curious, and looking for some reassurance in weight-gaining. thanks! 

How is it that people who weigh more than me fit into smaller sizes?  I am 5'5'' and around 125-130 lbs...I am a size 9 in pants and medium-large in shirts.  I am aiming for my "running" size-117- that's where I felt my best:)

it really just depends on your body type.

i am also 5'5 && weigh 114.

im not super skinny, but i am skinny.  you cant count my ribs, maybe one.  LOL

i have a flat stomach but im working on trying to get it not to like jiggle when i walk.  >:[    

im a 3-4 in pants and a small-large in shirts. depends on the store