I care for my girlfriend, whom I have been seeing for a few months now. I have no problem maintaining an erection when she performs oral sex on me. In fact I can climax twice in a relatively short time. We have, however, been unable to actually engage in intercourse, since when we go to put on the condom, I lose my erection. I'm not really having too much of a problem getting erect (i.e., I get an erection, and may lose it early on, but I am able to get and maintain another one for oral sex). What could be the problem? Stress? A lack of physical attraction? I will be grateful for any answer you can provide me.