Eating chocolate, sweet stuff and carb laden food is an addiction - I suffer from it and tend to lurch from one diet to another. For me, I hated myself when binging but felt compelled to do so and that made me feel worse - anxious about my appearance, not wanting to go out etc etc. I could still easily sit and eat a whole pack of penguins at one sitting but have found ways to stop myself most of the time.
You will get energy spikes from all the sugar, then horrendous lows that make you reach for more food and it is possible that you are simply not getting the right vitamins and nutrients your body needs.
You don't sound massively overweight - I'm 5 ft 3 and weigh 12st 10, (and dieting) and I can fit comfortably into size 16's and some 14's.
First step is to rule out any underlying medical condition - get thee to a GP and make sure that your hunger / dizziness / anxiety is not potentially a hormonal (thyroid) issue that can be diagnosed with a blood test and easily managed with tablets.
Weaning yourself off choc and stuff is never ever easy - I did it a few months ago by going cold turkey on the Cambridge Diet - meal replacements so you can just train your brain not to allow any food for yourself and not worry about meal plans etc. By day 3, you are detoxing and losing any hunger pangs. After a couple of weeks, your tastes change, your stomach has shrunk and you will be back in control. With that diet, you see a diet counsellor in their home, so you can have a chat about food triggers etc.
Your GP may recommend other methods, but that is what I would do - cut everything out and then gradually re-introduce good food - easier to do in the Summer when it is warm.
Try some exercise aswell - a good brisk walk in the fresh air should hopefully lift your mood and be far more effective than a choc bar aswell as being diversionary - can you get out to the park or something next time you get the urge to snack ? I have become addicted to the gym instead and spend most evenings there, leaving less time to be tempted to eat.
Good luck