i need some suggestions

i am a 15 year old girl every single diet that i have tried has failed im thinking about going on weight watchers. but one diet that did work is the milk diet with the 24 24 milk . com thing i lost like 20 pounds but even then i ganed it all back. now i am in high school i [u]dont have a way to get to a gym except when i have pe[/u]. and where i live there are no side walks and the streets have blind spots so i cant go walking or running. so if anyone has a simple way of losing weight with out much excersize i would very much like that.