I'm 5ft 8 and am usually 9.5 stone and a size 10. That's my comfortable ideal weight.
When I was 20, (living abroad and not doing a lot) my weight crept up to 11.5 stone and I felt really over weight. I was a size 12-14. I started getting dimply arms and felt really self conscious. Came home, went back to 9.5 stone and felt comfortable again.
It's a personal thing- I don't look at others who are 12-14 and think they're overweight, or think anything at all. But I personally feel overweight when I don't fit a size 10. I've always been very self critical...