Self conscious :(

Emily
So recently I have been feeling very self conscious. I have put on a lot of weight, but I have always been quite a big girl since I am naturally very curvy with big thighs and big breasts. I go to a girls boarding school and the food we are fed is really not healthy, and we have no other choice unless we would like to starve! (For example lunch today was lasagne and dinner was pasta). We are not allowed to join gyms either because we aren't allowed to leave school grounds, but I would really like to loose weight! We are given slice every afternoon and desert every night, I stop myself from eating it most days but it is so tempting! I have been feeling very depressed about my figure lately and even afraid to show my boyfriend of one year anymore :( can someone please help me with ideas to get myself on track?