On being "skinny"

I was always a 'pudgy' little girl, ever since i was little until about my freshman/sophmore year of high school. I never cared much about my weight, I ate when I was hungry and didn't care about what anyone else thought of me.
Then I got skinny (not by trying, my 'babyfat' just wore off I guess..) and I still ate when I was hungry and didn't care what people thought. No one really commented or cared and that was just fine with me.
Now, on to after I've gotten married and had 2 kids, apparently i'm supposed to be fat, because everyone and their mother thinks it's ok to comment on my weight. Seriously, I've been the same height and weight since my junior year of HIGH SCHOOL. I get that some peoples metabolism slows down as they get older/have kids, but I am one of the lucky few that hasn't happened to (yet!). I still eat when i'm hungry, hey, I even eat sometimes when i'm NOT hungry, I don't excersice that often (unless you count cleaning house and taking care of the kids excersicing). Just like everyone else, I do gain an extra 5-10lbs during the holidays, cause I eat extra sweets and extra meals wherever I go, but by january/feb i'm back to my normal weight because I don't continue to overindulge.
What i'm saying here is that yes, I am one of the lucky few that is naturally skinny without having to work at it, and that's just the thing, people comment on my weight like it's something that I have worked to achieve and that is BAD.
It's gotten to the point where if I know that I am going out to eat for dinner, I will eat a small lunch that way I can eat something big, because I KNOW if i eat a normal lunch, and go out to eat, the portions are so big, I will usually only eat half, and then who ever i'm with will say something about me not eating and my weight.
I don't eat that many healthy things either, so far I have had pizza for dinner last night, pizza for breakfast, and guess what i had for lunch? yup, some nice hot greasy fattening pizza. and i have a half a twix bar calling my name right in front of me too.
You know what I do with popcorn? I pop it in the microwave, put it in a bowl, melt some butter in a cup and pour the butter all over the popcorn till it shrivles up and then i eat the popcorn with a spoon, it's like a heart attack in a bowl, cause isn't that what all anorexic chicks do?!