Psychological stress, performance anxiety, depression, neurogenic disorders, body image issues, medications, alcohol, smoking, drugs/medications, hormonal imbalance,
kidney failure, metabolic disorders, hypertension, diabetes, prostatitis, urethritis etc. just to name a few. Anxiety and stress play an important role in the development of erectile dysfunction; and is the most common possible cause. At a primary level, I would suggest being a bit relaxed and working on the psychological factors.