Bulimia please help!?

So, this winter i went from 53 kgs to 55 and im NOT happy about it at all. And a week ago i've been throwing up everything i eat and now i have an eating disorder and am considered bulimic. But the thing is i know it's wrong but i've become addicted to it.... so i was wonder why it is that after i throw up i end up being a kg larger than i actually am and then in the morning im a kg lighter? also how long will it take for me 2 loose about 5 kgs before summer 09-010??