The explanation is not elaborate. From your history we could think you are have general fatigue. There are numerous causes for this
3) Chronic fatigue syndrome
The things like Reducing stress, Good sleep, Balanced Nutrition, Daily Exercise, Cutting down the habit of Smoking
and Alcohol (if any) , Finding a hobby fulfilling your interest, taking a break from the routine can help you. If you are heavily exhausted and are not as energetic as earlier , it would be prudent to see a General Physician who can assess your case.