Small, but chubby tummy. WTH

Okay, I'm thin but far from anorexic. I'm 16 and only weigh 102lbs, eat a lot, and have always had a flat tummy and high metabolism. It's been like this for ever but recently I got a layer of chub on my stomach that sticks out and I HATE IT! I tried working out and doing sit ups but nothings really helping. Plus if I don't eat enough my stomach hurts so diets are a bad idea. Is there something I should /change/ in my diet that doesn't involve eating less or some kind of workout that with target that area of just fat in general?
Small, but chubby tummy. WTH
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