Why have I gained weight??!?

Dieting only helps you to lose weight if you exercise along with the dieting. You made the mistake of skipping meals and this resulted in your weight gain. Eating regular balanced meals boost your metabolism, but skipping meals and undernourishing your body signaled your brain to "hibernation" mode, telling your body to store all the food you ate into fat, instead of using the energy quickly. If you want to lose that weight, go back to eating a healthy 1000-1500 calories a day (a balanced diet) and exercising for at least an hour a day.