Last night I was with a girl who really enjoyed the experience. Unfortunately it wasn't mutual. I had no problem getting erect and staying that way for at least 30-45 min but in the end I couldn't ejaculate. I've had problems in the past with just getting and maintaining a full erection. This only happens w/girls. I can always become erect and ejaculate when masturbating. In some ways it felt like an accomplishment just to be able to become immediately erect, keep it up for a long time and pleasure her. On the other hand, I still couldn't "close the deal". I'm a 22yr old college student, about average weight and generally healthy. Used to smoke marijuana but haven't in over a year and a half. I do drink semi frequently and had drunk just over 5 beers the night I described. However, in the past i've had the same problems when I had not drank any alcohol. Responses/advice are very much appreciated.

Mark