I am a "recovering" anorexic. I want to know how you can loose weight without my dietician knowing?

I got out of treatment at the beginning of June and I now weigh a whopping 98 pounds when I am 13 and only 5'3 (I used to weigh like 40 some pounds less)! I need to know how to loose some of the weight so I am at least 85 - 90 pounds without my dietician knowing or my parents. If they figure out I am going to have to go back to inpatient treatment and get a feeding tube! Please I need to loose some weight without ANYONE knowing. PLEASE HELP A FAT GIRL OUT!!!!!!!!!!!!!!!!