Expert answer:
It may well be the anxiety of the moment or it may be sexual impotence. Remember to always use protection.
I'm 16 years old, and I've tried to take my virginity twice. I go to my girlfriend's house, we start on the couch (up to that beauty, my penis gets hard), when I take her to bed and I go for the condom it gets soft, I have problem? I am worried.
It may well be the anxiety of the moment or it may be sexual impotence. Remember to always use protection.