So my doctor told me to eat 500-800 calories a day?!ahhhhhhhhhhhhhhh how can i possibly do this?!!?

Well being that you were an athlete im sure you have some kind of self-control and to lower you eating habits in such a drastic way its going to take every bit of self control. One way to help is to not have so much high calorie food at home and not to have as much food at home period so that there wont be a lot accessible. You would have to go to the grocery store more but then you wouldn't have as much to always get your hands on. You could also find some kind of hobby or activity to keep your mind off eating, like taking a cl at a community college, volunteering or some other kind of activity. When you get the urge to binge eat you could go take a walk or something else like that.