Hello dear Understand your concern. Do not think excessive regarding erection problem it cause depression and psychiatric problem and performance anxiety, depression are the most common cause of erectile dysfunction. For sexual intercourse it is not necessary you will require large penis. There is no relationship between size of penis and sexual intercourse. How can you tell you have erection problem without doing sex. Just be relax, take healthy diet, fresh fruits, anti oxidant tablet like Co Q, start regular exercise, avoid stress and thinking. If you have excessive fear for sake of gain you can do impotency test in infertility clinics. But first involve in sex and then if problem occur, go for test. Hope this may help you Best regards Dr. Sagar