i eat lots, but am i too skinny?

hi im a 16year old girl and i eat lots, im fortunate not to have to watch my weight but i'm 5"6 and 120 lbs. do you think thats too skiny? you can't see my ribs or anything at all and i have long legs. im very slim but you can see that im healthy. just wondering if maybe something is wrong with me as to why i have been 120lbs for the last 2 years and grew to 5"6. thanks. Annabelle xxx[/size 18]