The real key is a gradual modification to diet and exercise. All too often people go hard for the beginning and burn out really quickly. Our bodies are designed for adaption. We push to hard to lose weigh and our body adapts by storing more fat as a defense mechanism. Do it gradually and your body gets used to operating like that and you will see positive results.
As for diet, don't try to starve yourself. Caloric restriction is really hard on your body both physically and mentally, so it's something you need to ease into. My advise for eating right (1.) Cut the sugar. It is the major enemy here. It makes you put on weight more than anything and deeply affects mood. (2.) Eat more fat and protein. This will keep you full for longer and will actually promote fat loss. I lost about 18kg in only a few months while eating steak and eggs for breakfast every day.
I have battled with weight all my life, all my life, so I know how you feel physically and emotionally! I have lost and gained, lost and gained etc., If you want some sound advice message me, let talk seriously about this. You will need ongoing support and I am happy to offer that. :-)
lets start with the easy part first. start a food log. write down what you eat & time. how much. do this for a month. from there you can start to make changes you can live with. anything short term will not last. that way you will not be repeating the cycle of lost and gain again. be honest to yourself with the food log. i have been there & still fighting it. you will need to create a new life style with food. god lucky sweetie