Wow, this will be a long post (brace yourself)...
I have struggled with this issue a lot. When I was in high school, I weighed about 150 lbs. (I'm 5'7") and was convinced I was fat. I wore somewhat baggy clothes, didn't like to wear clothes that had a lot of shape, because I was convinced that I was "fat." The fact is, the line of women in my family gives me wide hips, large breasts, a round face w/ a big nose, muscular legs and shoulders, and a soft little pooch under my stomach that will never go away (so says my svelte mother, who after 22 years of wedded bliss and three kids can STILL fit into her wedding dress). I finally had to just learn to accept how I look. (Not that I always do, but it's progress!) Oddly, 3 years after feeling "fat" at 150 lbs. in high school, I feel prettier (at 182 pounds!) than I ever have before. Granted, that's not the healthiest weight I could be. This year I resolved that if I could lose 3 pounds each month, I'd be at a very ideal shape/size come next Christmas. My doctor says that my ideal weight for my height is 135 lbs... I smile and nod but if I can be 150 lbs, I'll still be fabulously curvy and quite healthy.
I was talking with a friend just the other day about when I first took yoga and what a great instructor I had. I was describing this woman, who was in her mid-60s, in great shape but not really "skinny," fairly small-chested, had an abundance of laugh lines and who wore her waist-length grey hair up in a twisty bun. I was saying how she is the most gorgeous woman I've ever met - she truly is. Her beauty radiated from such a deep place inside - she was so at ease with herself and comfortable in her own skin. No magazine would put her on the cover - a size 8 (I'm guessing here), wrinkles, grey hair - but she had a calming presence and a genuine smile that I'll never forget.
Avatar - Isaac, my blue-fronted Amazon parrot. Adopted 9/7/07. Age 30 (my pet is older than me!)