Thanks for posting your query.
You have not given many details about your physical health. It would be helpful to know more about your problems.
1. Have you been diagnosed with any illness?
2. What is your height and weight?
3. How long have you been feeling unhealthy?
4. Are you studying? If yes, how do you fare in your studies?
5. Have you any symptoms like sudden loss of weight, loss of appetite etc.?
Anyway I will try to help you with the information given.
Eat regular balanced meals with lots of fresh vegetables and fruits in it. Drink milk daily. Regular exercise helps build muscles as well as improves mood. Eat lots of protein rich food.
It would be best if you could get a personal diet chart prepared for you by a dietitian addressing your calorie requirements.
Becosule one daily at night.
Start with these measures and you will hopefully see a difference in your life.
If you feel depressed in spite of this, then it would be best if you visit your doctor and discuss your problems with him.
Wishing you good health.