How to overcome childhood fatigue?

Hello doctor,

I have been suffering from severe fatigue since childhood. I feel tired even without doing anything, feel like I did too much work or studied too much. I cannot study even for three hours with proper dedication and concentration, as a result, my student life is not successful. If I try to study five hours a day, the next day I feel very tired and weak throughout the day and this tiredness remains for three to four days. When I am fatigued, my thoughts become negative, I feel like I cannot do anything in life, and sometimes I think about ending my life. Sometimes I think if I could do things with proper dedication and concentration, I could achieve many things in life. During Fatigue, I also experience problems in proper breathing. I consulted a doctor, but he could not understand my problems. He advised me to eat some vitamin capsules and prescribed me some medicine but the results did not satisfy me. Even during exam time, I cannot study sometimes because of tiredness and weaknesses, and I am even fatigued writing exams. Please help.

Thank you.