how to develop a positive body image and healthy relationship with food?

For starters, i'm 18, female, am 5'3 and weigh 107 lbs...today (planning on being 103 soon hopefully).  I HATE how I look.  I almost always want to cry when I step on the scale or look in a mirror.  I obssess over reflections and mirrors, always comparing different ones in hopes that one time i will be happy with what i see, but of course i never am.  I feel guilty eating food.  if i go over 800 calories, or eat more of one food group than my exchange method diet allows me to i pretty much cry myself to sleep and have a terrible day the next day.  i have to have at least four cups of green tea a day or else i'm afraid i'm going to get bloated and look heavier.  i feel really guilty eating even normal food, and when i eat junk, or more than i need i feel like a terrible person.  I have a very unhealthy relationship with food, that i know.  i think about it ALL the time.  i obssess over calories and foods and nutrition facts, and if my clothes are any tighter than they were the other day.  i'm always concerned that i havent burned enough calories for the day.  i feel like i'm just always getting fatter and i need to prevent it and that the only way i'll be skinny is too relaly over do it, but whenever i do that i end up binging and ruining everything!  i have nightmares about my weight ALL the time.  i have weird dreams about scales and embarassing weigh ins too, and sometimes i have dreams that i'm as thin as i want to be and then i wake up and feel depressed.  i hate how i look, i dont want people to see my face because i dont want people to see the fat in it.  

i am a ballet dancer, and i get embarassed to wear my leotard, and i'm embarassed to tell people that i'm a dancer, because dancers are supposed to be skinny and i'm not:(

i am auditioning for jobs in ballet companies this winter and i am so so so SOOOO afraid that i'm going to see all my years of hard work and training crumble because i'm too heavy and nobody will hire me.  i am desperately afraid that my body issues will keep me from getting a job oppurtunity.

i'm so stressed and worried about it i don't even know what to do anymore, but i can't live like this anymore:(