I'm 21 years old and have been dating my girlfriend for 2 years. I never have any problem at all getting an erection around her. We used to date on and off in high school. During one of these "off" times I was with another girl. We went to fool around one time and I couldn't even get an erection even though she was really attractive to me. I honestly feel that I can only get an erection around my girlfriend and no other girl. I can get an erection by myself or looking at porn but I am almost positive if some beautiful girl came up to me and wanted to fool around, that I would not be able to get an erection. I feel that if I were to break up with my girlfriend, that it would take forever (if at all) to get an erection with a new girl. Is this just a psychological problem or possibly a medical one? Thanks a lot for the help.