Can your body prevent weight loss?

Options
Hello,

My name is savannah. I'm 5'4 and 120 lbs with a goal weight of 105. I was recently sick- no throw ups or diarrhea, but some headaches and loss of appetite- and lost 5lbs, bringing me down to 115. I was so happy! But two days after ( eating roughly 1000 cal per day) I gained back all the weight lost! This has happened before. Does my body just want to stay at 120? Is there a way to lose any more weight??