Start small.
Forget about calories, and start by thinking what you can add IN to your diet to make it more nutritious.
So if you eat cereal and toast for breakfast, add some eggs and tomatoes.
If you eat soup and a sandwich and crisps for lunch, add in some cooked chicken.
If you eat spaghetti bolognese for dinner, add some broccoli and spinach.
This will regulate your blood sugar - nothing is going to work until you do that because the sugar has messed it up.
Next step - make some swaps. If you normally have a piece of cake or donut have some almonds and dark chocolate instead. Replace the cereal with some avocado or Greek yogurt.
Baby steps and adding in rather than taking away is the key.
And please please don’t count calories! Calories are the unit of energy the food has, which is completely irrelevant here. Here’s an example: a chocolate digestive has 84 calories. An egg has 155. But the digestive will spike your blood sugar, make you crave more and will (over time) harm your body - including your immune system and your metabolism - due to the trans fats etc. The egg has good protein and fat and will keep you feeling full and fuel your body.
Do NOT count calories, count nutrition. You will feel fuller, have more energy and you will gradually stop craving sugar.