Without any major trauma ,illness , associated medical or surgical conditions, your problem of Erectile dysfunction is more likely to be psychological .
Psychological causes can be many like , performance anxiety , lack of adequate stimulation, monotony in act, reduced interest , dispute ,differences etc...
Consult a Psychiatrist and explore the cause and take proper treatment. Don't waste precious time of active youth , enjoy an active sexual life .
Next Steps
Consult a Psychiatrist
Health Tips
Don't try to take medicines by yourself , might help temporarily but will keep the cause unresolved