In young people forgetfulness is usually a sign of anxiety or depression. Occasionally other underlying medical causes can be there like issues with
thyroid,
B12 or folaate deficiency or other chronic medical or neurological causes. I suggest you consult a psychiatrist who can take proper history, examine and order appropriate tests. If it is anxiety or depression related, things improve upon appropriate treatment with psychological counselling, lifestyle modifications and in some cases medicine too. Regards