Hi. I am 21 years old and have a question. Whenever i am sexually aroused i get a natural hard erection and within some moment of so my penis releases the pre-cum. But just after the release i begin to lose my natural erection and even after that if i try to keep my penis up i have to do it manually which is by masturbating but even after that i get a mild erection which is not at all as hard as the previous one. I cant understand why. Is this a problem or it is normal?