Your fatigue may be due to poor sleep hygiene. Try to manage your time better to get more sleep and limit your phone or computer use before bed. Eat healthy foods and remember to drink water (lack of water can affect feelings of fatigue).
Raise your energies. Also forcefully participating in any activity in which you have no interest in will drain you far more than anything else. If that is the case for you, either find a way to make what you're studying more interesting, or if you truly have no interest in it, do something else.