what is the cause of weak erection, my penis sometimes do not get up and if it does it wont be hard to go in....sometimes it gets hard and when am busy it dies again or I will ejaculate in a very short of time. I am scared of my girl friend these days, she acts as if she is fine with it but I can see she is not...I am even scared to act or to tell her that we must make love cause I know my erection keeps dying...what must i do