What Causes Loss Of Memory Due To Lack Of Concentration?

hi doctor, I am 23 years old male and have serious some problem as I'm forgetting things alot and this has been happening from last 2 to 3 years. Further I cannot concentrate on things that's why I am unable to remember. As this has made me frustrate because day by day I am losing my memory due to this several mistakes are happening now. Please advise how to deal with it. Best regards. Xyz