Hi, Welcome to Health care magic forum.
First thing you have to do is to change the mind set. You must be studying, and a teenager, you would have learn t many things from the surrounding people, and the books.
Nothing is impossible, and there is always some thing which is causing the change of the life style, and there will a way to over come it.
The causes may be the
anemia, deficiency of Harmon,
vitamins, etc.
I advise you to consult a physician for diagnosis and treatment .
You may need to have tests of blood, and urine for diagnosis.
Take more of green leafy vegetables, pulses, sprouts, and protein rich foods,to have good health, recovery, and resistance.
Wishing for a quick and complete recovery. Thank you.