When i try to restrict calories and carbs i get a pressure feeling in chest and throat....what could this be.?

Low blood sugar: We need calories and carbohydrates to function. Low carb diet combined with restricted calories likely is likely putting you in to low blood sugar and/or ketoacidosis. This feels icky...Nauseous, tired, no energy and your breath may take on a fruity unpleasant smell. This means you have used all of your glucose stores. A modified low carb diet is much healthier especially if you are active.

Chest pressure: Not necessarily from low sugar you can confirm by measuring your sugar with a finger stick test although there are several important causes of chest pain, among which is heart disease, anxiety does typically cause throat and chest discomfort and the anxiety may be driven by your fear that depriving yourself of carbs is doing something bad.