Eating 300-500 calories a day and weighing 90 lbs at a height of 5'5 will not make you skinny, it will make you anorexic. You wont look like Beckham or Mary-Kate, you will look like an ugly shriveled prune. You already know how unhealthy this is but you will also look really bad. Your weight right now if perfectly fine, dont try to become underweight because its VERY unattractive and VERY unhealthy. Just stay with the weight you have and if you have an eating disorder then try to get some help. Its good that you went from 80 lbs to 118, which shows that you have control over your disorder, but dont let it control you.
Good luck, I'm sure that you look fine and if you feel uncomfortable with the way you look then post a picture of yourself, perhaps all you need is a little reassurance=)
PS: Victoria Beckham and Mary-Kate Olsen are very attractive but they dont weight 80 lbs! If they did then they would be horribly ugly, trust me anoriexic girls are EXTREMELY unattractive.
Ever heard of Isabelle Caro? She is a woman with anorexia. Be the judge for yourself, is she attractive?
http://img.metro.co.uk/i/pix/2007/09/isa…
Below is a link to Mary-Kate Olsen. She had some trouble with anorexia but such a beautiful woman would never risk her looks with such an eating disorder. She has gotten help and maintains a reasonable weight.
http://tv.popcrunch.com/wp-content/uploa…