Weight weight weight

Ok so my whole life I have been painfully skinny. & always been told to eat more and to gain weight. It was hard ! So hard ! My weight used to go up and down all the time. I could go days with out eatting very little and didn't enjoy food. Now that my lungs are good I have gained more and more and more weight. 5 years ago I was a painfully skinny size 6 and was fitting into children's clothes and it bothered me. I didn't feel womanly , I wasn't curvy and nothing I wore fitted properly. Five years on, I have gone from a size 8, to at the moment a size 10 and maybe some times a 12! Everyone says I look great and I look healthy. But it a big shock to the system when I look in the mirror and have to buy bigger clothes. When I was younger I never thought I would ever ever watch my weight ! I could eat anything and not gain any weight. Now I gain weight just by looking at a chocolate bar !. It's not that I feel fat exactly , and I'm dieting no way. But I know I really don't want to get much bigger. It's so hard finding the right balance of eatting all the calories you need in the day for a healthy cf diet but how so you know when to stop eatting. Gosh.