How to get an erection when drunk

Q: Hi, I’m 19 and i’m experiencing a problem getting erections before sex. When i’m fooling around with a girl i’m usually rock hard right up until we start taking our clothes off. Then by the time we’re about to have sex i’ve gone soft and cant get hard again. The only time i’ve ever been able to have sex before is when I was drunk because it takes the nervous factor out of the...