I am 24 years old.. When I'm having sex with my partner I'm rock solid at first, and then few minutes later my penis starts to go soft I try my best to keep it hard, i try thinking of stuff that turn me on but it doesn't work,, And there was one time I could not get my  penis hard at ALL!!! I really wanted to have sex but could not get hard I'm only 24 what's going on Can some one tell me what's going on with it