The funniest paradox on earth

Ok, I don't get it.
Everyone keeps telling me stop being so obsessed with my weight and to stop whining about it and that I look prettier now and "no need to diet lah!"and blah blah blah.
Then WHY (oh why) at the end of the day, does everyone also tell me (IN THE SAME SENTENCE FURTHERMORE) that

I've put on weight???!!!

Seriously, am I never going to hear the end of it?
"Wah, you've put on so much weight... but still so pretty lah" (from my uncle so all I could do was smile weakly).
"Keshia, you've put on weight! You look good. Last time you were too skinny" (this one's at least nice about it).
"Hey Keshia, Taiwan food must be very delicious right? You must have eaten a lot there" (subtle... but you get the message).

This one happened yesterday:
Me: XXXXX, you look so pretty! You've lost weight! .
XXXXX: You leh, you've put on weight.
That was it. Not even a, "You look better now" or something nice to add to it. Quite a a good thing I'm quite "thick-skin" so I wasn't too offended because this one was quite... unintentionally offensive

At least more people are calling me pretty, considering what an "ugly duckling" I am.
So everyone listen- unless someone can explain to me this paradox, then keep quiet about me talking about my weight and blah blah blah. You think I'm not tired about always being so conscientious about my weight? Hello, I'm not as lucky to be born with my Dad's genes (my sisters, esp. Abish took all his eat-anything-but-can-still-lose-weight-by-sleeping-one-night genes), so I have to settle with losing weight the whining, pathetic, painful way- DIET DIET DIET (and some exercise when I'm in the mood to :p). Dancing would help if I there were dances like, every 2 days or something (in my dreams).

Meanwhile, my official diet is a low-carbs-low-sugar diet, esp. for dinner. Depending on where I'm eating (I'm ironically more self-destructive eating at home becasue at home I can control better and eat close to NO carbs at all for dinner), I'll modify accordingly. If it can work when I was in JC, I have hopes it'll still work now.