My girlfriend and I have been having sex for about 4 months now. This past Saturday we had sex 6 times. When we first got together I was unable to get an erection the first and second times. I think it was nerves. I visited my doctor and he prescribed viagra. I used the drug 8-10 times, then stopped. I didn't need it anymore. Lastnight we were getting ready to have sex, I was fully erect. I was pleasuring her and felt myself loosing my erection. She pulled me on top of her and was discusted to see I had lost my erection. She feels that there is a reason for this and it's not just something that happens. Does it happen or not. By the way I am 27.I was not on Viagra on Saturday.