Don't know why I couldn't get hard
A few months ago my girlfriend went down on me and for some reason I couldn't get hard. In fact since we had been kissing and for a long time, I had had an erection, but after I started to get wet, I think pre-ejaculation, she went down on me and my erection went away completely and I couldn't get hard. Ever since that moment I have been extremely confused because I don't know why it happened and it has been occupying my thoughts excessively, and it has effected me so much that I have even started to steer clear of some sexual encounters and come ons to prevent that possible embarrassment again. I am 18, a virgin, and I don't have any problem masturbating. What is wrong with me? Please help, and thank you in advance for your input.