It is very strange
Do you remain upset due to some reason?
Do you eat properly?
Do you feel sick some time?
Please go to the doctor for check up.
Try to learn by writing. In this way you remember well.
PRAY 5 times &read QURAN daily with translation.
Learn by heart last 10 SURA of QURAN.
QURAN is such a book when you read your memory will increase.