I could be wrong for sure, and a capable doctor is what you really need, but I am thinking MAYBE it's a tapeworm. Especially if you have traveled outside the country recently or before this started.
see if hard candy in your pocket carry a lot if that changes things then you got hyperglycemia.opposite of diabetes.
It could be diabetic related.
Have you checked your pressure, blood, cholesterol, sugar etc?
It is extremely important to see your Dr. and request Blood Work.
Also, I am not sure if you are on some sort of diet, but to me, it seems like you arent getting enough nutrients.
Is your blood pressure quite low? Have it checked at a chemist early in the morning.
Then have a glass of electrolite solution. If your blood pressure is low you feel tired and wan and your body may think food will help but of course it won't.
I have heard of people eating but with no salt and/or fat in their diet and they feel pretty wretched.
If your electrolites and other minerals and vitamins are balanced you could possibly feel better,
All the best