I've been with my girlfriend for several months now. The sex has been great. We probably have sex 3-4 times a week. The only issue is that I am good for only one round at a time. I'm completely satisfied with having one orgasm, and am honestly pretty spent after that. From time to time she initiates another round 10-15 minutes later. I can usually get aroused and erect, but it will take me way too long cum the second time. Do most people out there have sex multiple times in one "sitting?" If so any advice? Thanks.