If you're unable to go to the gym, you can look up videos on weight loss online and choose one or more based on your personal requirements. Also, you will have to be a little conscious about what you're eating and how many calories you're consuming as opposed to how many calories you're losing. (Doesn't mean you should go about calculating the cal, it's more about choosing healthy which usually tends to have less calories than processed foods in general) Perhaps you can start with consciously walking 10,000+ steps to get yourself in the mood for exercise. ++ it is absolutely normal to have a fluctuating weight during your teenage (and throughout life in general) so don't beat yourself up over it <3