Erectile Dysfunction

[Vincenso]

I am 20 years old. Up until around December of last year, I had no problems getting an erection and keeping it. I could be rock hard for as long as I wanted to. In december, a friend and I had been at a party and we both had quite a bit to drink. Later that night when we went to have sex, I couldn't get it up. I thought, too much booze, no biggie right? We decided to just try again in the morning, but when we woke up, the same thing happened. I could get it up for a minute or two, but it would not remain full and wained after that until i had no control over it whatsoever. I think this is psychological because I have absolutely no problem getting a full erection for masturbation. I also get erections when I am making out/really close with a girl, but when the time comes it just goes flat.. I don't get it. Does anyone have any advice on who I should talk to about this problem? I am in good health and have suffered no physical injuries that would cause this so I'm almost positive it's psychological.