Thank you for posting your query at DoctorSpring.com
At age 20 years old patientthe most common reason for an event of erectile dysfunction is psychological. For proper sexual function to develop, one needs proper functioning and coordination of the genitals and the state of mind. If there is any problem with the state of mind, then erectile dysfunction develops. At age 20 years, its very unlikely to develop erectile dysfunction due to organic reasons. The most common reason being anxiety and stress due to the relationship issues with the partner.
I would suggest you should meet a psychiatrist/psychologist along with your partner to analyze various relationship issues.
Hope this helps
If you need any further clarifications, do let me know.
Dr. Srikanth Reddy MD