I'm 18 years old and currently have a girlfriend. One day me and my girlfriend were about to have sex, but then something REALLY REALLY embarassing happened... my erection died. I can get an erection perfectly fine when I'm by myself but for some reason when it comes to sex, my erection goes about 50-60% then dies. I don't know why, but I need to resolve this issue ASAP. Please help.. anyone. I'm a virgin btw..