My parents force me to eat, even when I'm full?

Please, please help... I am crying in pain right now... My parents always make me eat whenever they want me to... And usually, that's after a meal or something, so I'm already full... :'( I don't like eating when I'm full... :'( It feels terrible, as I am naturally a person with a small appetite... I gain up to 3 pounds a day because of them, and I want to stay healthy and fit, and not get fat like they are... :'( Please... I am currently 89 pounds, though I was 86 yesterday... My body naturally sheds the extra pounds within a week, but then they force more pounds on me... I want to be healthy! They make me eat junk food like cupcakes right before bed!! :'( Please, help! They always say things like"You're growing, Naiya." or "Ooh, but skinny is so ugly! Chubby is cute!". You see, I naturally have a very quick metabolism, so I am still, fortunately fit and thin... But I fear that I will not be if this continues... I've tried talking to them calmly about this, but they say "Yes, but did you know many girls your age become anorexic? That could happen to you, too!". And, no, I would NOT become anorexic! I hate the look of being all bony! Though you can see my ribcage currently, I am still in the very middle of a healthy weight range. ...And also, the pain... It hurts... They will force me to stuff my face until I can barely walk... Right now, I am in serious pain... I am nauseous and bloated... :'( ...I hate it... Please, help! What do I do?!?!