Margypops is right, you need to have your blood sugar tested.
You might want to get your B vitamins checked also. If your low on them you can feel dizzy, exhausted and cold.
Are you getting enough protein?
Really, the best thing to do is see your Dr to find out what's going on. They can check you sugar right in the office. Take care. Remar
what is your eating pattern like, have you eaten when the symptoms appear? it could be low blood sugar , Hypoglycemia , if you feel like that eat something ,some carb item, a sandwich and see if you feel better .,if it continues see the Doctor .