Relax. Its okay to masturbate frequently in teens, as your body is making you do it, by giving sexual desire, every few hours
Masturbation is normal. It doesnot harm your body or the penis
Sperm production in males continues for long time till ripe old age
You are just 20, so dont get worried
Next Steps
Right now you must stop watching porn or doing 'habitual' masturbation. As days pass you will yourself see your body responding by giving you good erections.
Right now worry is causing the problem, so stop worrying.
Health Tips
Erections happen due to increased blood flow to penis. Regular exercise can help improve your blood flow and help you get better erections.